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May 2008

Water Availability in the Goulburn-BrokenA report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project

Murray-Darling Basin Sustainable Yields Project acknowledgments

The Murray-Darling Basin Sustainable Yields project is being undertaken by CSIRO under the Australian Government's Raising National

Water Standards Program, administered by the National Water Commission. Important aspects of the work were undertaken by Sinclair

Knight Merz; Resource & Environmental Management Pty Ltd; Department of Water and Energy (New South Wales); Department of

Natural Resources and Water (Queensland); Murray-Darling Basin Commission; Department of Water, Land and Biodiversity

Conservation (South Australia); Bureau of Rural Sciences; Salient Solutions Australia Pty Ltd; eWater Cooperative Research Centre;

University of Melbourne; Webb, McKeown and Associates Pty Ltd; and several individual sub-contractors.

Murray-Darling Basin Sustainable Yields Project disclaimers

Derived from or contains data and/or software provided by the Organisations. The Organisations give no warranty in relation to the data

and/or software they provided (including accuracy, reliability, completeness, currency or suitability) and accept no liability (including

without limitation, liability in negligence) for any loss, damage or costs (including consequential damage) relating to any use or reliance

on that data or software including any material derived from that data and software. Data must not be used for direct marketing or be

used in breach of the privacy laws. Organisations include: Department of Water, Land and Biodiversity Conservation (South Australia),

Department of Sustainability and Environment (Victoria), Department of Water and Energy (New South Wales), Department of Natural

Resources and Water (Queensland), Murray-Darling Basin Commission.

CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader

is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or

actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the

extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences,

including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using

this publication (in part or in whole) and any information or material contained in it. Data is assumed to be correct as received from the

Organisations.

Citation

CSIRO (2008). Water availability in the Goulburn-Broken. A report to the Australian Government from the CSIRO Murray-Darling Basin

Sustainable Yields Project. CSIRO, Australia. 132pp.

Publication Details

Published by CSIRO © 2008 all rights reserved. This work is copyright. Apart from any use as permitted under the Copyright Act 1968,

no part may be reproduced by any process without prior written permission from CSIRO.

ISSN 1835-095X

Photo on cover: Dickie Swamp, north of Tungamah, Victoria. Courtesy of the Goulburn-Broken Catchment Management Authority,

Victoria

Director’s Foreword

Following the November 2006 Summit on the Southern Murray-Darling Basin, the then Prime Minister and

Murray-Darling Basin state Premiers commissioned CSIRO to report on sustainable yields of surface and groundwater

systems within the Murray-Darling Basin. This report from the CSIRO Murray-Darling Basin Sustainable Yields Project

details the assessments for one of 18 regions that encompass the Basin.

The CSIRO Murray-Darling Basin Sustainable Yields Project is providing critical information on current and likely future

water availability. This information will help governments, industry and communities consider the environmental, social

and economic aspects of the sustainable use and management of the precious water assets of the Murray-Darling Basin.

The project is the first rigorous attempt worldwide to estimate the impacts of catchment development, changing

groundwater extraction, climate variability and anticipated climate change, on water resources at a basin-scale, explicitly

considering the connectivity of surface and groundwater systems. To do this, we are undertaking the most

comprehensive hydrologic modelling ever attempted for the entire Basin, using rainfall-runoff models, groundwater

recharge models, river system models and groundwater models, and considering all upstream-downstream and surface-

subsurface connections. We are complementing this work with detailed surface water accounting across the Basin –

never before has surface water accounting been done in such detail in Australia, over such a large area, and integrating

so many different data sources.

To deliver on the project CSIRO is drawing on the scientific leadership and technical expertise of national and state

government agencies in Queensland, New South Wales, Victoria, the Australian Capital Territory and South Australia, as

well as the Murray-Darling Basin Commission and Australia’s leading industry consultants. The project is dependent on

the cooperative participation of over 15 government and private sector organisations contributing over 100 individuals.

The project has established a comprehensive but efficient process of internal and external quality assurance on all the

work performed and all the results delivered, including advice from senior academic, industry and government experts.

The project is led by the Water for a Healthy Country Flagship, a CSIRO-led research initiative which was set up to

deliver the science required for sustainable management of water resources in Australia. The Flagship goal is to achieve

a tenfold increase in the social, economic and environmental benefits from water by 2025. By building the capacity and

capability required to deliver on this ambitious goal, the Flagship is ideally positioned to accept the challenge presented

by this complex integrative project.

CSIRO has given the Murray-Darling Basin Sustainable Yields Project its highest priority. It is in that context that I am

very pleased and proud to commend this report to the Australian Government.

Dr Tom Hatton

Director, Water for a Healthy Country

National Research Flagships

CSIRO

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Executive Summary

Background

The CSIRO Murray-Darling Basin Sustainable Yields Project is providing governments with a robust estimate of water

availability for the entire Murray-Darling Basin (MDB) on an individual catchment and aquifer basis, taking into account

climate change and other risks. This report describes the assessment undertaken for the Goulburn-Broken region. While

key aspects of the assessment and modelling methods used in the project are contained in this report, fuller

methodological descriptions will be provided in a series of project technical reports.

The Goulburn-Broken region is in north-central Victoria and covers 2.1 percent of the total area of the MDB. The region is

based around the Goulburn and Broken rivers. The population is 144,000 or 7 percent of the MDB total, concentrated in

the centres of Shepparton, Nagambie, Benalla, Kyabram and Tatura. About half the region is devoted to dryland cereal

cropping and grazing, and about one-twelfth is irrigated dairy pasture and horticultural cropping. An extensive irrigated

area stretches from south and east of Shepparton to west of Tatura and Kyabram. Approximately 177,600 ha were

irrigated in 2000 including 158,800 ha for pastures and hay and 8600 ha for orchard production. The lower Goulburn

River and the floodplain downstream of Loch Garry are listed as nationally important wetlands. The river influences the

Ramsar listed Barmah-Millewa Forest and Gunbower Forest wetlands during periods of high flow.

The region generates approximately 11 percent of the runoff within the MDB. The rainfall and runoff (and the fraction of

rainfall that becomes runoff) in the Goulburn-Broken region, particularly in the southern parts, are amongst the highest in

the MDB. The region accounts for around 14 percent of the surface water diverted for irrigation in the MDB and

5.4 percent of the total groundwater used in the MDB.

Key Messages

The key messages relating to climate, surface water resources, groundwater and the environment are presented below

for scenarios of current and possible future conditions. The scenarios assessed are defined in Chapter 1. Scenario A is

the baseline against which other scenarios are compared.

Historical climate and current development (Scenario A)

The annual rainfall and runoff averaged over the region is 764 mm and 149 mm, respectively. The current average

annual surface water availability for the region is 3233 GL/year. Current average surface water diversions (including

water supplied and channel and pipe losses) within the Goulburn-Broken region are 1099 GL/year. A further 507 GL/year

is transferred to the Campaspe, Loddon-Avoca and Wimmera regions via the Waranga Western Channel. The relative

level of surface water use for the region is defined as the ratio of total surface water diversions (including water

transferred to other regions) to water availability. The current relative level of surface water use is extremely high at

50 percent. The degree of flow regulation is high for the Goulburn River but much lower for the Broken River.

Reliability of supply is determined separately for high reliability water shares (HRWS) and low reliability water shares

(LRWS) and is reported for allocations in February. In the regulated Goulburn system, a 100 percent HRWS allocation

occurs in 97 percent of years and the minimum HRWS allocation is 73 percent. A 100 percent LRWS allocation occurs in

42 percent of years and a zero LRWS allocation occurs in 24 percent of years. In the regulated Broken system, a 100

percent HRWS allocation occurs in 88 percent of years and the minimum HRWS allocation is 1 percent. A 100 percent

LRWS allocation occurs in 84 percent of years and a zero LRWS allocation occurs in 11 percent of years.

Groundwater extraction in the region for 2004/05 is estimated at 92 GL. About 87 percent of this extraction came from

the Shepparton Groundwater Management Unit (GMU) (which is a Water Supply Protection Area). Current groundwater

extraction is moderate (37 percent of recharge) in the Shepparton and Alexandra GMUs. Much of the pumping from the

Shepparton GMU is sourced from reduced groundwater evapotranspiration – a significant fraction of the groundwater is

pumped for salinity control and a reduction in evapotranspiration is the intended consequence. Current extraction is low

in the other GMUs in the region.

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Current groundwater use represents 10 percent of total water use on average and 16 percent of total water use in years

of lowest surface water diversion. Surface–groundwater connectivity mapping indicates that the Goulburn River is

gaining along most of its length, but losing over two small sections – upstream of the Goulburn Weir and downstream of

Loch Garry. Broken Creek is losing at a moderate rate over most of its length. The Broken River is considered to be

gaining at a high rate downstream of Orrvale. The total average impact of the current level of groundwater use will be an

eventual 20 GL/year loss of streamflow to groundwater with most of this occurring by 2010.

Water resources development has increased more than four-fold the average period between large (1000 GL/month)

beneficial floods to the lower Goulburn River floodplain. Additionally, undesirably low flows that diminish deep water

pools and degrade native fish habitat are now more prevalent – occurring about twice a year on average rather than

once every 7 to 8 years under without-development conditions.

Recent climate and current development (Scenario B)

The average annual rainfall and runoff over the past ten years (1997 to 2006) were 15 and 41 percent lower respectively

than the long-term (1895 to 2006) average values.

If the climate of the last ten years were to continue, average surface water availability would be reduced by 41 percent

and end-of-system flows on the Goulburn River at McCoy’s Bridge would be reduced by 58 percent. The volume of water

diverted for use within the region would be reduced by 25 percent. In the regulated Goulburn system, a 100 percent

HRWS allocation would occur in 49 percent of years and the minimum HRWS allocation would be 8 percent. A 100

percent LRWS allocation would occur in 2 percent of years and a zero LRWS allocation would occur in 88 percent of

years. In the regulated Broken system, a 100 percent HRWS allocation would occur in 52 percent of years and the

minimum HRWS allocation would be 1 percent. A 100 percent LRWS allocation would occur in 48 percent of years and a

zero LRWS allocation would occur in 47 percent of years. Transfers to other regions via the Waranga Western Channel

would be reduced by 25 percent. The relative level of use for the region would rise to 63 percent.

Under a continuation of the climate of the last ten years, the lower Goulburn River floodplain would cease to receive

large flood events leading to serious ecological consequences. This climate would also increase the occurrence of

undesirably low flows in the lower Goulburn River which would further degrade the habitat value of the deep pools on the

lower river, with consequences for endangered fish species.

Future climate and current development (Scenario C)

Rainfall-runoff modelling with climate change projections from global climate models indicates that future runoff in the

region will decrease significantly. Under the best estimate (median) 2030 climate there would be a reduction in average

annual runoff of 13 percent. The extreme estimate ranges from a 44 to a 2 percent reduction in average annual runoff.

Under the best estimate (or median) 2030 climate, average surface water availability would be reduced by 14 percent

and end-of-system flows at McCoy’s Bridge would be reduced by 22 percent. Water diversion for use within the region

would decrease by 5 percent. In the regulated Goulburn system, a 100 percent HRWS allocation would occur in

87 percent of years and the minimum HRWS allocation would be 29 percent. A 100 percent LRWS allocation would

occur in 21 percent of years and a zero LRWS allocation would occur in 36 percent of years. In the regulated Broken

system, a 100 percent HRWS allocation would occur in 83 percent of years and the minimum HRWS allocation would be

1 percent. A 100 percent LRWS allocation would occur in 79 percent of years and a zero LRWS allocation would occur in

17 percent of years. Transfers to regions via the Waranga Western Channel would be reduced by 5 percent. The relative

level of use for the region would rise to 54 percent.

Under the wet 2030 climate extreme, average surface water availability would be reduced by 3 percent. Overall, there

would be little impact on the volume of water diverted for use or on the reliability of supply. However, Goulburn River

outflows would be reduced by 5 percent. Under the dry 2030 climate extreme, conditions would be slightly more severe

than under a continuation of the climate of the last ten years. Water availability would be reduced by 45 percent, water

use within the region would be reduced by 29 percent, end-of-system flows on the Goulburn would be reduced by

62 percent and the volumes of water transferred out of the region via the Waranga Western Channel would be reduced

by 32 percent. Reliability of supply would be similar to a continuation of the recent climate for the Broken system but

would be substantially worse for the Goulburn system. For example, in the Goulburn system a 100 percent HRWS

allocation would occur in 33 percent of years and the minimum HRWS allocation would be 4 percent.

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The best estimate 2030 climate would see substantial reductions in the occurrence and volumes of flooding of the lower

river floodplain and the occurrence of undesirably low flows would increase slightly. The dry 2030 climate extreme would

lead to similar hydrological changes and ecological consequences as a continuation of the recent climate. The wet 2030

climate extreme would mean little change from current conditions for flooding of the lower river floodplain; however, the

occurrence of undesirably low flows would increase slightly.

Future climate and future development (Scenario D)

Projected growth in commercial forestry plantations is negligible. The total farm dam storage volume is projected to

increase by 8.7 GL or 8 percent by 2030. This would reduce mean annual runoff by about 0.5 percent. The best estimate

of the combined impact of climate change and farm dam development would be a 14 percent reduction in average

annual runoff. Extreme estimates range from a 44 to a 3 percent reduction. This minor change would have very little

impact on surface water diversions within the region or other components of the regional water balance.

The projected average groundwater extraction by 2030 is 154 GL/year. This is an increase of 67 percent over current

levels. Most of the increase in groundwater extraction is expected to occur in the Shepparton GMU where extraction

(under the best estimate 2030 climate) would then be 64 percent of recharge. Increases in extraction would raise the

level of development in the modelled Nagambie GMU and in the unmodelled Kinglake GMU from low to moderate.

Extraction from the modelled Kialla and Goorambat GMUs would remain at low levels, while extraction from the

unmodelled Alexandra GMU would increase to a high level. The total eventual impact of groundwater extraction at

projected 2030 levels would be an average streamflow reduction of 37 GL/year and 12 GL/year of this would be due to

increases in groundwater extraction outside of the modelled Southern Riverine Plains area.

The projected farm dam and groundwater development would have negligible impact on surface water use and reliability

of supply and the environmentally important aspects of the river flow regime that have been assessed for the lower

Goulburn River.

Uncertainty

The runoff estimates for the region are relatively accurate because there are many gauged catchments from which to

estimate the model parameter values. The largest sources of uncertainty for future climate results are the climate change

projections (global warming level) and the modelled implications of global warming on regional rainfall. The results from

15 global climate models were used but there are large differences amongst these models in terms of regional rainfall

predictions. There are also considerable uncertainties associated with the future projections of farm dams and

commercial forestry plantations. Future developments could differ considerably from these projections if governments

were to impose different policy controls.

The Goulburn-Broken river model reproduces observed streamflow patterns very well and estimates water balance terms

that were similar to the water accounts. The model provides moderately to very strong evidence of changes in flow

pattern related to the dry and best estimate variants of the 2030 climate. Evidence for change under the wet variants was

weak to modest. The model provides reasonable to strong evidence of changes in flow pattern related to development in

the Goulburn River but not in the Broken River. The changes due to projected development are less than 2 percent of

predicted climate changes. Overall the model is well suited for the purpose of this project. Predictions of changes in low

flow patterns are assigned a low level of confidence.

The Southern Riverine Plain groundwater model, developed for this project, was run in a without-development calibration

and used for assessment of higher priority GMUs. It was peer-reviewed but it has not received widespread scrutiny.

Lateral flows from outside the modelled area are small. The grid size is 1000 m, coarser than other models. The model

was assessed as thorough and is adequate for providing information on water availability in the context of this project. It

is less reliable for local management requirements. The model reached a dynamic equilibrium under all scenarios. The

reliability of predictions could be improved to ‘very thorough’ by recognising the importance of this groundwater resource.

The simple water balances used at assess the other GMUs have a high uncertainty.

The environmental assessments of this project only consider a subset of the important assets for this region and are

based on limited hydrology parameters with no direct quantitative relationships for environmental responses.

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Considerably more detailed investigation is required to provide the necessary information for informed management of

the environmental assets of the region.

© CSIRO 2008 May 2008 Water availability in the Goulburn-Broken

Table of Contents

1 Introduction............................................................................................................................... 1 1.1 Background..................................................................................................................................................................1 1.2 Project methodological framework................................................................................................................................3 1.3 Climate and development scenarios.............................................................................................................................4 1.4 Rainfall-runoff modelling...............................................................................................................................................5 1.5 River system modelling ................................................................................................................................................7 1.6 Monthly water accounts................................................................................................................................................9 1.7 Groundwater modelling ..............................................................................................................................................11 1.8 Environmental assessment.........................................................................................................................................12 1.9 References.................................................................................................................................................................12

2 Overview of the region .......................................................................................................... 14 2.1 The region..................................................................................................................................................................14 2.2 Environmental description ..........................................................................................................................................18 2.3 Surface water resources.............................................................................................................................................19 2.4 Groundwater ..............................................................................................................................................................22 2.5 References.................................................................................................................................................................26

3 Rainfall-runoff modelling ....................................................................................................... 28 3.1 Summary....................................................................................................................................................................28 3.2 Modelling approach ....................................................................................................................................................29 3.3 Modelling results ........................................................................................................................................................33 3.4 Discussion of key findings ..........................................................................................................................................38 3.5 References.................................................................................................................................................................39

4 River system modelling.......................................................................................................... 40 4.1 Summary....................................................................................................................................................................40 4.2 Modelling approach ....................................................................................................................................................42 4.3 Modelling results ........................................................................................................................................................47 4.4 Discussion of key findings ..........................................................................................................................................65 4.5 References.................................................................................................................................................................66

5 Uncertainty in surface water modelling results................................................................... 66 5.1 Summary....................................................................................................................................................................66 5.2 Approach....................................................................................................................................................................67 5.3 Results .......................................................................................................................................................................71 5.4 Discussion of key findings ..........................................................................................................................................81 5.5 References.................................................................................................................................................................82

6 Groundwater assessment...................................................................................................... 83 6.1 Summary....................................................................................................................................................................83 6.2 Groundwater management units.................................................................................................................................84 6.3 Surface–groundwater connectivity..............................................................................................................................89 6.4 Recharge modelling ...................................................................................................................................................91 6.5 Groundwater modelling ..............................................................................................................................................93 6.6 Modelling results ........................................................................................................................................................95 6.7 Water balances for groundwater management units not modelled and unincorporated areas...................................104 6.8 Conjunctive water use indicator................................................................................................................................106 6.9 Discussion of key findings ........................................................................................................................................107 6.10 References...............................................................................................................................................................107

7 Environment .......................................................................................................................... 108 7.1 Summary..................................................................................................................................................................108 7.2 Approach..................................................................................................................................................................109 7.3 Results .....................................................................................................................................................................112 7.4 Discussion of key findings ........................................................................................................................................112 7.5 References...............................................................................................................................................................113

Appendix A Rainfall-runoff results for all subcatchments.......................................................... 115

Appendix B River modelling reach mass balances .................................................................. 117

Appendix C River system model uncertainty assessment by reach ....................................... 124

Water availability in the Goulburn-Broken May 2008 © CSIRO 2008

Tables

Table 1-1. River system models in the Murray-Darling Basin ...........................................................................................................7 Table 2-1. Summary of land use in the year 2000 within the Goulburn-Broken region....................................................................17 Table 2-2. Ramsar wetlands and wetlands of national significance located within the Goulburn-Broken region .............................19 Table 2-3. Summary of surface water sharing arrangements .........................................................................................................21 Table 2-4. Categorisation of groundwater management units, including annual extraction, entitlement and recharge details .........25 Table 2-5. Summary of groundwater management plans ...............................................................................................................25 Table 2-6. Annual groundwater extraction within the Goulburn-Broken region ...............................................................................26 Table 3-1. Summary results under the 45 Scenario C simulations (numbers show percentage change in mean annual rainfall and runoff for Scenario C relative to Scenario A) for the Loddon-Avoca, Campaspe and Goulburn-Broken regions..............................35 Table 3-2. Water balance over the entire region by scenario..........................................................................................................37 Table 4-1. Storages in the river model in the Goulburn-Broken region ...........................................................................................45 Table 4-2. Water use configuration in the model ............................................................................................................................45 Table 4-3. Water management in the model ..................................................................................................................................45 Table 4-4. Rainfall, evaporation and flow factors for model robustness trial run .............................................................................46 Table 4-5. Model setup information................................................................................................................................................47 Table 4-6. River system model average annual water balance in the Goulburn-Broken region under scenarios O, A, B, C and D .49 Table 4-7. Average annual water balance for the Waranga Western Channel under scenarios A, B, C and D ...............................50 Table 4-8. Average annual surface water availability downstream McCoy’s Bridge under scenarios A, B and C (assessed for without-development conditions, which for Scenario A is synonymous with Scenario P) ................................................................52 Table 4-9. Details of storage behaviour in the Goulburn-Broken region..........................................................................................53 Table 4-10. Change in total water use in each subcatchment relative to Scenario A ......................................................................54 Table 4-11. Annual total surface water use under scenarios A, B, C and D....................................................................................57 Table 4-12. Level of water use under scenarios A, B, C and D ......................................................................................................57 Table 4-13. Cease-to-flow at mid-system locations in percentage time under scenarios P, A, B, C and D......................................61 Table 4-14. Monthly flow event frequency for mid system locations Broken River at the confluence with Goulburn River and Goulburn River upstream of Goulburn Weir under scenarios P, A, B, C and D...............................................................................62 Table 4-15. Cease-to-flow at Goulburn River downstream of McCoy’s Bridge (end-of-system) in percentage time under scenarios P, A, B, C and D ............................................................................................................................................................63 Table 4-16. Monthly flow event frequency at Goulburn River downstream of McCoy’s Bridge (end-of-system) under scenarios P, A, B, C and D ............................................................................................................................................................63 Table 4-17. Relative level of available water not diverted for use under scenarios A, B, C and D...................................................64 Table 4-18. Inter-region comparison of water supply reliability under scenarios A, B and C ...........................................................65 Table 5-1. Framework for considering implications of assessed uncertainties................................................................................68 Table 5-2. Comparison of water accounting reaches with reach codes used in runoff modelling....................................................69 Table 5-3. Some characteristics of the gauging network of the Goulburn-Broken region (22,378 km2) compared with the entire Murray-Darling Basin (1,062,443 km2) ...........................................................................................................................................71 Table 5-4. Streamflow gauging stations for which data were used in the Goulburn-Broken REALM model ....................................74 Table 5-5. Regional water balance modelled and estimated on the basis of water accounting.......................................................77 Table 6-1. Groundwater entitlements and current and future extractions for Goulburn-Broken region ............................................86 Table 6-2. Summary results from the 45 Scenario C simulations. Numbers show percentage change in mean annual rainfall and recharge under Scenario C relative to Scenario A. Those in bold type have been selected for further modelling. ..........................93 Table 6-3. Change in recharge applied to model scenarios under scenarios B and C ....................................................................94 Table 6-4. Definition of groundwater indicators ..............................................................................................................................95 Table 6-5. Groundwater balance for the area of the Goulburn-Broken region covered by the Southern Riverine groundwater model under without-development scenario and scenarios A, B, C and D ................................................................................................96 Table 6-6. Median groundwater level under Scenario A, and changes from this level under scenarios B, C and D ........................97 Table 6-7. Average annual water balance for the Shepparton GMU under scenarios A, B, C and D ..............................................98 Table 6-8. Groundwater indicators for the Shepparton GMU under scenarios A, B, C and D .......................................................100 Table 6-9. Groundwater level in the Goorambat GMU under Scenario A, and changes from this level under scenarios B, C, D...100 Table 6-10. Average annual water balance in the Goorambat GMU under scenarios A, B, C and D ............................................101 Table 6-11. Groundwater indicators for the Goorombat GMU under scenarios A, B, C and D......................................................101 Table 6-12. Median groundwater level in the Kialla GMU under Scenario A, and changes from this level under scenarios B, C and D .................................................................................................................................................................................................102 Table 6-13. Average annual water balance for the Kialla GMU under scenarios A, B, C and D....................................................102 Table 6-14. Groundwater indicators for the Kialla GMU under scenarios A, B, C and D...............................................................102 Table 6-15. Median groundwater level in individual bores in the Nagambie GMU under Scenario A, and changes from this level under scenarios B, C and D.........................................................................................................................................................103 Table 6-16. Average annual water balance for the Nagambie GMU under scenarios A, B, C and D ............................................103

© CSIRO 2008 May 2008 Water availability in the Goulburn-Broken

Table 6-17. Groundwater indicators for the Nagambie GMU under scenarios A, B, C and D........................................................104 Table 6-18. Estimated groundwater extraction for the southern parts of the Goulburn-Broken region ..........................................104 Table 6-19. Recharge in low priority groundwater management units under scenarios A, B, C and D..........................................105 Table 6-20. Environmental indicator (ratio of extraction to recharge) groundwater management units not modelled, and unincorporated areas under scenarios A, B, C and D ..................................................................................................................106 Table 6-21. Conjunctive water use indicator: ratio of groundwater to total water diversion in the Goulburn-Broken region on average and in 1-, 3- and 5-year periods of lowest surface water diversions under scenarios A, B, C and D ...............................107 Table 7-1. Definition of environmental indicators..........................................................................................................................111 Table 7-2. Environmental indicator values under scenarios P and A, and percentage change (from Scenario A) in indicator values under scenarios B, C and D. In the drier scenarios there are no events (n.e.) and hence the volume indicators cannot be calculated and the percentage change in period indicators are not meaningful. Negative percentage changes indicate reductions.....................................................................................................................................................................................................112

Figures

Figure 1-1. Region by region map of the Murray-Darling Basin ........................................................................................................2 Figure 1-2. Methodological framework for the Murray-Darling Basin Sustainable Yields Project ......................................................3 Figure 1-3. Timeline of groundwater use and resultant impact on river.............................................................................................8 Figure 2-1. 1895–2006 annual and monthly rainfall averaged over the region. The curve on the annual graph shows the low frequency variability. ......................................................................................................................................................................15 Figure 2-2. Map of dominant land uses of the Goulburn-Broken region with inset showing the region’s location within the Murray-Darling Basin. The map only shows assets that are assessed in the project (Chapter 7) and that fall within the region. A full list of key assets associated with the region is in Table 2-2............................................................................................................16 Figure 2-3. Historical surface water diversions from the Goulburn and Broken river catchments ....................................................22 Figure 2-4. Map of groundwater management units within the Goulburn-Broken region.................................................................24 Figure 3-1. Map of the modelling subcatchments and calibration catchments ................................................................................30 Figure 3-2. Modelled and observed monthly runoff and daily flow duration curve for the calibration catchments ............................32 Figure 3-3. Spatial distribution of mean annual rainfall and modelled runoff averaged over 1895–2006 .........................................33 Figure 3-4. 1895–2006 annual rainfall and modelled runoff averaged over the region (the curve shows the low frequency variability) ......................................................................................................................................................................................34 Figure 3-5. Mean monthly rainfall and modelled runoff (averaged over 1895–2006 for the region).................................................34 Figure 3-6. Percentage change in mean annual runoff under the 45 Scenario C simulations (15 GCMs and three global warming scenarios) relative to Scenario A runoff for the Loddon-Avoca, Campaspe and Goulburn-Broken regions .....................................35 Figure 3-7. Mean annual rainfall and modelled runoff under scenarios A, Cdry, Cmid and Cwet ....................................................36 Figure 3-8. Mean monthly rainfall and modelled runoff under scenarios A, C and D averaged over 1895–2006 across the region (C range is based on the consideration of each month separately – the lower and upper limits in C range are therefore not the same as scenarios Cdry and Cwet) ...............................................................................................................................................38 Figure 3-9. Daily flow duration curves under scenarios A, C and D averaged over the region (C range is based on the consideration of each rainfall and runoff percentile separately – the lower and upper limits in C range are therefore not the same as scenarios Cdry and Cwet) .........................................................................................................................................................38 Figure 4-1. The full extent of the Goulburn Simulation Model across the Goulburn-Broken, Campaspe and Loddon-Avoca regions, indicating how the Waranga Western Chanel links across the three regions ..................................................................................43 Figure 4-2. River system map showing subcatchments, inflow and demand nodes and gauge locations within the Goulburn-Broken region ............................................................................................................................................................................................44 Figure 4-3. Transect of total river flow for without-development conditions under scenarios A, B and C.........................................51 Figure 4-4. Water availability for the region under Scenario A........................................................................................................52 Figure 4-5. Difference in annual water availability for the region under scenarios B and C relative to Scenario A...........................52 Figure 4-6. Total Goulburn-Broken headworks storage behaviour over the period of lowest storage content under (a) scenarios A and B, (b) scenarios Cwet, Cmid and Cdry and (c) scenarios Dwet, Dmid and Ddry ......................................................................53 Figure 4-7. Average annual water use from upstream to downstream Goulburn River under (a) scenarios A, B and C and (b) scenarios A, B and D................................................................................................................................................................54 Figure 4-8. Total water use under (a) Scenario A and difference from Scenario A in total water use under (b) Scenarios B, (c) Scenario Cwet, (d) Scenario Dwet, (e) Scenario Cmid, (f) Scenario Dmid, (g) Scenario Cdry and (h) Scenario Ddry.....................56 Figure 4-9. Reliability of (a) High Reliability Water Share and (b) Low Reliability Water Share supply in the Goulburn-Broken River system for Goulburn Irrigation Areas and Private Diverters; (c) Goulburn Urbans; and (d) High Reliability Water Share and (e) Low Reliability Water Share Broken Private Diverters under scenarios A, B, C and D...........................................................................58 Figure 4-10. Total volume of water use as a percentage of demand for the Goulburn-Broken region under (a) scenarios A, B and C and (b) scenarios A, B and D.........................................................................................................................................................60 Figure 4-11. Monthly flow duration curves at Broken River upstream of the Goulburn confluence under (a) scenarios P, A, B and C and (b) scenarios P, A, B and D, and at Goulburn River upstream of Goulburn Weir under (c) scenarios P, A, B and C and (d) scenarios P, A, B and D ...........................................................................................................................................................61

Water availability in the Goulburn-Broken May 2008 © CSIRO 2008

Figure 4-12. Seasonal plots at Broken River upstream of the Goulburn confluence under (a) scenarios P, A, B and C, and (b) scenarios P, A, B and D and at Goulburn River upstream of Goulburn Weir under (c) scenarios P, A, B and C, and (d) scenarios P, A, B and D ...........................................................................................................................................................62 Figure 4-13. Monthly flow duration curves at Goulburn River downstream of McCoy’s Bridge (end-of-system) under (a) scenarios P, A, B and C, and (b) scenarios P, A, B and D..................................................................................................................................63 Figure 4-14. Seasonal plots at Goulburn River downstream of McCoy’s Bridge (end-of-system) under (a) scenarios P, A, B and C, and (b) scenarios P, A, B and D.....................................................................................................................................................64 Figure 4-15. Comparison of diverted and non-diverted shares of water under scenarios P, A, B, C and D.....................................64 Figure 5-1. Map showing the subcatchments used in modelling, and the water accounting reaches ..............................................69 Figure 5-2. Map showing the rainfall, stream flow and evaporation observation network, along with the subcatchments used in modelling .......................................................................................................................................................................................72 Figure 5-3. The fraction of inflows/gains, outflows/losses and the total of water balance components for each accounting reach that is (a) gauged or (b) could be attributed in the water accounts ........................................................................................................76 Figure 5-4. Changes in the model efficiency (the performance of the river model in explaining observed streamflow patterns) along the length of the river (numbers refer to reach) ..............................................................................................................................78 Figure 5-5. Simulated (model) and recorded (gauged) monthly streamflow in the lower Goulburn River at McCoy Bridge (Reach 7)......................................................................................................................................................................................................79 Figure 5-6. Pattern along the river (numbers refer to reach) of the ratio of the projected change over the river model uncertainty for (a) monthly and (b) annual flows under scenarios P, C and D........................................................................................................80 Figure 6-1. Location of groundwater management units in the region ............................................................................................85 Figure 6-2. Hydrograph for Bore 118893 completed in the fractured rock aquifer of the Goulburn-Broken highlands showing a declining trend in water level. Ground level is 312.27 m AHD. .......................................................................................................87 Figure 6-3. Hydrograph for Bore 88009 completed in the Renmark Group displaying a falling trend of up to 10m. Ground level is 99.8 m AHD...................................................................................................................................................................................87 Figure 6-4. Hydrograph for Bore 60074 completed in the highland valley Deep Lead Calivil Formation showing a rise in groundwater level. Ground level is 140.00 m AHD. ........................................................................................................................88 Figure 6-5. Hydrograph for Bore 46190 completed in the Deep Lead of the Calivil Formation in the Goulburn Catchment displaying a falling trend since the early 2000s. Ground level is 119.88 m AHD. ............................................................................................88 Figure 6-6. Hydrograph for Bore 109763 displaying rapid rises in water level consistent with flood recharge. Ground level is 128.17 m AHD. ..............................................................................................................................................................................89 Figure 6-7. Map of surface–groundwater connectivity ....................................................................................................................90 Figure 6-8. Comparison of Broken River level at Orrvale, with groundwater levels in two nearby bores. Since bores are located approximately 400 m downstream of the gauging station, levels have been uniformly increased by 0.5 m to account for changes in river level between the gauging station and the river adjacent to the bores. ...................................................................................91 Figure 6-9. Percentage change in mean annual recharge from the 45 Scenario C simulations (15 GCMs and three global warming scenarios) relative to Scenario A recharge.....................................................................................................................................92 Figure 6-10. Mass balance for the calibration model for the model area (Jan 1990 – Dec 2005; Inflows = Outflows) .....................94 Figure 6-11. Groundwater inflows to the Goulburn-Broken region under scenarios A, B, C and D..................................................96 Figure 6-12. Groundwater outflows from the Goulburn-Broken region under scenarios A, B, C and D ...........................................97 Figure 6-13. Groundwater inflows into the Shepparton GMU under scenarios A, B, C and D.........................................................98 Figure 6-14. Groundwater outflows from the Shepparton GMU under scenarios A, B, C and D .....................................................99 Figure 7-1. Location map of environmental assets .......................................................................................................................110 Figure 7-2. Satellite image of the lower Goulburn River and floodplain.........................................................................................111

© CSIRO 2008 May 2008 Water availability in the Goulburn-Broken ▪ 1

1 Introduction

1 Introduction

1.1 Background

Australia is the driest inhabited continent on Earth, and in many parts of the country – including the

Murray-Darling Basin – water for rural and urban use is comparatively scarce. Into the future, climate change and other

risks (including catchment development) are likely to exacerbate this situation and hence improved water resource data,

understanding and planning and management are of high priority for Australian communities, industries and

governments.

On 7 November, 2006, the then Prime Minister of Australia met with the First Ministers of Victoria, New South Wales,

South Australia and Queensland at a water summit focussed primarily on the future of the Murray-Darling Basin (MDB).

As an outcome of the Summit on the Southern Murray-Darling Basin, a joint communiqué called for “CSIRO to report

progressively by the end of 2007 on sustainable yields of surface and groundwater systems within the MDB, including an

examination of assumptions about sustainable yield in light of changes in climate and other issues”.

The subsequent Terms of Reference for what became the Murray-Darling Basin Sustainable Yields Project specifically

asked CSIRO to:

• estimate current and likely future water availability in each catchment and aquifer in the MDB considering:

o climate change and other risks

o surface–groundwater interactions

• compare the estimated current and future water availability to that required to meet the current levels of

extractive use.

The Murray-Darling Basin Sustainable Yields Project is reporting progressively on each of 18 contiguous regions that

comprise the entire MDB. These regions are primarily the drainage basins of the Murray and the Darling rivers –

Australia’s longest inland rivers, and their tributaries. The Darling flows southwards from southern Queensland into New

South Wales west of the Great Dividing Range into the Murray River in southern New South Wales. At the South

Australian border the Murray turns southwesterly eventually winding to the mouth below the Lower Lakes and the

Coorong. The regions for which the project assessments are being undertaken and reported are the Paroo, Warrego,

Condamine-Balonne, Moonie, Border Rivers, Gwydir, Namoi, Macquarie-Castlereagh, Barwon-Darling, Lachlan,

Murrumbidgee, Murray, Ovens, Goulburn-Broken, Campaspe, Loddon-Avoca, Wimmera and Eastern Mount Lofty

Ranges (see Figure 1-1).

2 ▪ Water availability in the Goulburn-Broken May 2008 © CSIRO 2008

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Figure 1-1. Region by region map of the Murray-Darling Basin

The Murray-Darling Basin Sustainable Yields Project will be the most comprehensive MDB-wide assessment of water

availability undertaken to-date. For the first time:

• daily rainfall-runoff modelling has been undertaken at high spatial resolution for a range of climate change and

development scenarios in a consistent manner for the entire MDB

• the hydrologic subcatchments required for detailed modelling have been precisely defined across the entire

MDB

• the hydrologic implications for water users and the environment by 2030 of the latest Intergovernmental Panel

on Climate Change climate projections, the likely increases in farm dams and commercial forestry plantations

and the expected increases in groundwater extraction have been assessed in detail (using all existing river

system and groundwater models as well new models developed within the project)

• river system modelling has included full consideration of the downstream implications of upstream changes

between multiple models and between different States, and quantification of the volumes of surface–

groundwater exchange

• detailed analyses of monthly water balances for the last ten to twenty years have been undertaken using

available streamflow and diversion data together with additional modelling including estimates of wetland

evapotranspiration and irrigation water use based on remote sensing imagery (to provide an independent cross-

check on the performance of river system models).


1 Introduction

The successful completion of these outcomes, among many others, relies heavily on a focussed collaborative and team-

oriented approach between CSIRO, State government natural resource management agencies, the Murray-Darling Basin

Commission, the Bureau of Rural Sciences, and leading consulting firms – each bringing their specialist knowledge and

expertise on the MDB to the project.

1.2 Project methodological framework

The methodological framework for the project is shown in Figure 1-2. This also indicates in which chapters of this report

the different aspects of the project assessments and results are presented.

Figure 1-2. Methodological framework for the Murray-Darling Basin Sustainable Yields Project

The first steps in the sequence of the project are definition of the reporting regions and their composite subcatchments,

and definition of the climate and development scenarios to be assessed (including generation of the time series of

climate data that describe these scenarios). The second steps are rainfall-runoff modelling and rainfall-recharge

modelling for which the inputs are the climate data for the different scenarios. Catchment development scenarios for farm

dams and commercial forestry plantations are modifiers of the modelled runoff time series.

Next, the runoff implications are propagated through river system models and the recharge implications propagated

through groundwater models – for the major groundwater resources – or considered in simpler assessments for minor

groundwater resources. The connectivity of surface and groundwater is assessed and the actual volumes of surface–

groundwater exchange under current and likely future groundwater extraction are quantified. Uncertainty levels of the

river system models are then assessed based on monthly water accounting.

The results of scenario outputs from the river system model are used to make limited hydrological assessments of

ecological relevance to key environmental assets. Finally, the implications of the scenarios for water availability and

water use under current water sharing arrangements are assessed, synthesised and reported.


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1.3 Climate and development scenarios

The project is assessing the following four scenarios of historical and future climate and current and future development,

all of which are defined by daily time series of climate variables based on different scalings of the historical 1895 to 2006

climate sequence:

• historical climate and current development

• recent climate and current development

• future climate and current development

• future climate and future development.

These scenarios are described in some detail below with full details provided in Chiew et al. (2008a).

1.3.1 Historical climate and current development

Historical climate and current development – referred to as ‘Scenario A’ – is the baseline against which other climate and

development scenarios are compared.

The historical daily rainfall time series data that are used are taken from the SILO Data Drill of the Queensland

Department of Natural Resources and Water database which provides data for a 0.05o x 0.05o (5 km x 5 km) grid across

the continent (Jeffrey et al., 2001; and www.nrm.qld.gov.au/silo). Areal potential evapotranspiration (PET) data are

calculated from the SILO climate surface using Morton’s wet environment evapotranspiration algorithms

(www.bom.gov.au/climate/averages; and Chiew and Leahy, 2003).

Current development for the rainfall-runoff modelling is the average of 1975 to 2005 land use and small farm dam

conditions. Current development for the river system modelling is the dams, weirs and licence entitlements in the latest

State agency models, updated to 2005 levels of large farm dams. Current development for groundwater models is 2004

to 2005 levels of licence entitlements. Surface–groundwater exchanges in the river and groundwater models represent

an equilibrium condition for the above levels of surface and groundwater development.

1.3.2 Recent climate and current development

Recent climate and current development – referred to as ‘Scenario B’ – is used for assessing future water availability

should the climate in the future prove to be similar to that of the last ten years. Climate data for 1997 to 2006 is used to

generate stochastic replicates of 112-year daily climate sequences. The replicate which best produces a mean annual

runoff value closest to the mean annual runoff for the period 1997 to 2006 is selected to define this scenario.

Scenario B is only analysed and reported upon where the mean annual runoff for the last ten years is statistically

significantly different to the long-term average.

1.3.3 Future climate and current development

Future climate and current development – referred to as ‘Scenario C’ – is used to assess the range of likely climate

conditions around the year 2030. Three global warming scenarios are analysed in 15 global climate models (GCM) to

provide a spectrum of 45 climate variants for the 2030. The scenario variants are derived from the latest modelling for the

fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC, 2007).

Two types of uncertainties in climate change projections are therefore taken into account: uncertainty in global warming

mainly due to projections of greenhouse gas emissions and global climate sensitivity to the projections; and uncertainty

in GCM modelling of climate over the MDB. Results from each GCM are analysed separately to estimate the change per

degree global warming in rainfall and other climate variables required to calculate PET. The change per degree of global

warming is then scaled by a high, medium and low global warming by 2030 relative to 1990 to obtain the changes in the

climate variables for the high, medium and low global warming scenarios. The future climate and current development

Scenario C considerations are therefore for 112-year rainfall and PET series for a greenhouse enhanced climate around

2030 relative to 1990 and not for a forecast climate at 2030.


1 Introduction

The method used to obtain the future climate and current development Scenario C climate series also takes into account

different changes in each of the four seasons as well as changes in the daily rainfall distribution. The consideration of

changes in the daily rainfall distribution is important because many GCMs indicate that extreme rainfall in an enhanced

greenhouse climate is likely to be more intense, even in some regions where projections indicate a decrease in mean

seasonal or annual rainfall. As the high rainfall events generate large runoff, the use of traditional methods that assumes

the entire rainfall distribution to change in the same way will lead to an underestimation of mean annual runoff in regions

where there is an increase, and an overestimation of the decrease in mean annual runoff where there is a decrease

(Chiew, 2006).

All 45 future climate and current development Scenario C variants are used in rainfall-runoff modelling; however, three

variants – a ‘dry’, a ‘mid’ (best estimate – median) and a ‘wet’ variant – are presented in more detail and are used in river

and groundwater modelling.

1.3.4 Future climate and future development

Future climate and future development – referred to as ‘Scenario D’ – considers the ‘dry, ‘mid’ and ‘wet’ climate variants

from the future climate and current development Scenario C together with likely expansions in farm dams and

commercial forestry plantations and the changes in groundwater extractions anticipated under existing groundwater

plans.

Farm dams here refer only to dams with their own water supply catchment, not those that store water diverted from a

nearby river, as the latter require licences and are usually already included within existing river system models. A 2030

farm dam development scenario for the MDB has been developed by considering current distribution and policy controls

and trends in farm dam expansion. The increase in farm dams in each subcatchment is estimated using simple

regression models that consider current farm dam distribution, trends in farm dam (Agrecon, 2005) or population growth

(Australian Bureau of Statistics, 2004; and Victorian Department of Sustainability and Enviroment (DSE), 2004) and

current policy controls (Queensland Government, 2000; New South Wales Government, 2000; Victoria Government,

1989; South Australia Government, 2004). Data on the current extent of farm dams is taken from the 2007 Geosciences

Australia ‘Man-made Hydrology’ GIS coverage and from the 2006 VicMap 1:25,000 topographic GIS coverage. The

former covers the eastern region of Queensland MDB and the northeastern and southern regions of the New South

Wales MDB. The latter data covers the entire Victorian MDB.

A 2030 scenario for commercial forestry plantations for the MDB has been developed using regional projections from the

Bureau of Rural Sciences which takes into account trends, policies and industry feedbacks. The increase in commercial

forestry plantations is then distributed to areas adjacent to existing plantations (which are not natural forest land use) with

the highest biomass productivity estimated from the PROMOD model (Battaglia and Sands, 1997).

Growth in groundwater extractions has been considered in the context of existing groundwater planning and sharing

arrangements and in consultation with State agencies. For groundwater the following issues have been considered:

• growth in groundwater extraction rates up to full allocation

• improvements in water use efficiency due to on-farm changes and lining of channels

• water buy-backs.

1.4 Rainfall-runoff modelling

The adopted approach provides a consistent way of modelling historical runoff across the MDB and assessing the

potential impacts of climate change and development on future runoff.

The lumped conceptual daily rainfall-runoff model, SIMHYD, with a Muskingum routing method (Chiew et al., 2002; Tan

et al., 2005), is used to estimate daily runoff at 0.05o grids (~ 5 km x 5 km) across the entire MDB for the four scenarios.


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The model is calibrated against 1975 to 2006 streamflow data from about 200 unregulated catchments of 50 km2 to

2000 km2 across the MDB (calibration catchments). Although unregulated, streamflow in these catchments for the

calibration period may in fact reflect some low levels of water diversion and the effects of historical land use change. The

calibration period is a compromise between a shorter period that would better represent current development and a

longer period that would better account for climatic variability. In the model calibration, the six parameters in SIMHYD are

optimised to maximise an objective function that incorporates the Nash-Sutcliffe efficiency (Nash and Sutcliffe, 1970) of

monthly runoff and daily flow duration curve, together with a constraint to ensure that the total modelled runoff over the

calibration period is within 5 percent of the total recorded runoff. The resulting optimised model parameters are therefore

identical for all cells within a calibration catchment.

The runoff for non-calibration catchments is modelled using optimised parameter values from the geographically closest

calibration catchment, provided there is a calibration catchment point within 250 km. Once again the parameter values

for each grid cell within a non-calibration catchment are identical. For catchments more than 250 km from a calibration

catchment default parameter values are used. The default parameter values are taken from the entire MDB modelling

run (identical parameters across the entire MDB are chosen to ensure a realistic runoff gradient across the drier parts of

the MDB) which best matched observed flows at calibration points. The places these ‘default’ values are used are

therefore all areas of very low runoff.

As the parameter values come from calibration against streamflow from 50 km2 to 2000 km2 catchments, the runoff

defined here is different, and can be much higher, than streamflow recorded over very large catchments where there can

be significant transmission losses (particularly in the western and northwestern parts of the MDB). Almost all of the

catchments available for model calibration are in the higher runoff areas in the eastern and southern parts of the MDB.

Runoff estimates are therefore generally more accurate in the eastern and southern parts of the MDB and are

comparatively poor elsewhere.

The same model parameter values are used for all the simulations. The future climate Scenario C simulations therefore

do not take into account the effect on forest water use of global warming and enhanced atmospheric CO2 concentrations.

There are compensating positive and negative global warming impacts on forest water use, and it is difficult to estimate

the net effect because of the complex climate-biosphere-atmosphere interactions and feedbacks. This is discussed in

Marcar et al. (2006) and in Chiew et al. (2008b).

Bushfire frequency is also likely to increase under the future climate Scenario C. In local areas where bushfires occur,

runoff would reduce significantly as forests regrow. However, the impact on runoff averaged over an entire reporting

region is unlikely to be significant (see Chiew et al., 2008b).

For Scenario D (future climate and future development scenario) the impact of additional farm dams on runoff is

modelled using the CHEAT model (Nathan et al., 2005) which takes into account rainfall, evaporation, demands, inflows

and spills. The impact of additional plantations on runoff is modelled using the FCFC model (Forest Cover Flow Change)

(Brown et al, 2006; www.toolkit.net.au/fcfc).

The rainfall-runoff model SIMHYD is used because it is simple and has relatively few parameters and, for the purpose of

this project, provides a consistent basis (that is automated and reproducible) for modelling historical runoff across the

entire MDB and for assessing the potential impacts of climate change and development on future runoff. It is possible

that, in data-rich areas, specific calibration of SIMHYD or more complex rainfall-runoff models based on expert

judgement and local knowledge as carried out by some state agencies would lead to better model calibration for the

specific modelling objectives of the area. Chiew et al. (2008b) provide a more detailed description of the rainfall-runoff

modelling, including details of model calibration, cross-verification and regionalisation with both the SIMHYD and

Sacramento rainfall-runoff models and simulation of climate change and development impacts on runoff.


1 Introduction

1.5 River system modelling

The project is using river system models that encapsulate descriptions of current infrastructure, water demands, and

water management and sharing rules to assess the implications of the changes in inflows described above on the

reliability of water supply to users. Given the time constraints of the project and the need to link the assessments to State

water planning processes, it is necessary to use the river system models currently used by State agencies, the

Murray-Darling Basin Commission and Snowy Hydro Ltd. The main models in use are IQQM, REALM, MSM-Bigmod,

WaterCress and a model of the Snowy Mountains Hydro-electric Scheme.

The modelled runoff series from SIMHYD are not used directly as subcatchment inflows in these river system models

because this would violate the calibrations of the river system models already undertaken by State agencies to different

runoff series. Instead, the relative differences between the daily flow duration curves of the historical climate Scenario A

and the remaining scenarios (scenarios B, C and D respectively) are used to modify the existing inflows series in the

river system models (separately for each season). The scenarios B, C and D inflow series for the river system modelling

therefore have the same daily sequences – but different amounts – as the Scenario A river system modelling series.

Table 1-1. River system models in the Murray-Darling Basin

Model Description Rivers modelled

IQQM Integrated Quantity-Quality Model: hydrologic modelling tool developed by the NSW Government for use in planning and evaluating water resource management policies.

Paroo, Warrego, Condamine-Balonne (Upper, Mid, Lower), Nebine, Moonie, Border Rivers, Gwydir, Peel, Namoi, Castlereagh, Macquarie, Marthaguy, Bogan, Lachlan, Murrumbidgee, Barwon-Darling

REALM Resource Allocation Model: water supply system simulation tool package for modelling water supply systems configured as a network of nodes and carriers representing reservoirs, demand centres, waterways, pipes, etc.

Ovens (Upper, Lower), Goulburn, Wimmera, Avoca, ACT water supply.

MSM-BigMod Murray Simulation Model and the daily forecasting model BigMod: purpose-built by the Murray-Darling Basin Commission to manage the Murray River system. MSM is a monthly model that includes the complex Murray accounting rules. The outputs from MSM form the inputs to BigMod, which is the daily routing engine that simulates the movement of water.

Murray

WaterCress Water Community Resource Evaluation and Simulation System: PC-based water management platform incorporating generic and specific hydrological models and functionalities for use in assessing water resources and designing and evaluating water management systems.

Eastern Mt Lofty Ranges (six separate catchments)

SMHS Snowy Mountains Hydro-electric Scheme model: purpose built by Snowy Hydro Ltd to guide the planning and operation of the SMHS.

Snowy Mountains Hydro-electric Scheme

A few areas of the MDB have not previously been modelled and hence some new IQQM or REALM models have been

implemented. In some cases ancillary models are used to estimate aspects of water demands of use in the river system

model. An example is the PRIDE model used to estimate irrigation for Victorian REALM models.

River systems that do not receive inflows or transfers from upstream or adjacent river systems are modelled

independently. This is the case for most of the river systems in the MDB and for these rivers the modelling steps are:

• model configuration

• model warm-up to set initial values for all storages in the model, including public and private dams and tanks,

river reaches and soil moisture in irrigation areas

• using scenario climate and inflow time series, run the river model for all climate and development scenarios


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• where relevant, extract initial estimates of surface–groundwater exchanges and provide this to the groundwater

model

• where relevant, use revised estimates of surface–groundwater exchanges from groundwater models and re-run

the river model for all scenarios.

For river systems that receive inflows or transfers from upstream or adjacent river systems, model inputs for each

scenario were taken from the upstream models. In a few cases several iterations were required between upstream and

downstream models because of the complexities of the water management arrangements. An example is the

connections between the Murray, Murrumbidgee and Goulburn regions and the Snowy Mountains Hydro-electric Scheme.

For all scenarios, the river models are run for the 111-year period 1 July 1895 to 30 June 2006. This period therefore

ignores the first and last six months of the 112-year period considered in the climate analyses and the rainfall-runoff

modelling.

1.5.1 Surface–groundwater interactions

The project explicitly considers and quantifies the water exchanges between rivers and groundwater systems. The

approaches used are described below.

The river models used by State agencies have typically been calibrated by State agencies to achieve mass balance

within calibration reaches over relatively short time periods. When the models are run for extended periods the

relationships derived during calibration are assumed to hold for the full modelling period. In many cases, however, the

calibration period is a period of changing groundwater extraction and a period of changing impact of this extraction on the

river system. That is, the calibration period is often one of changing hydrologic relationships, a period when the river and

groundwater systems have not fully adjusted to the current level of groundwater development. To provide a consistent

equilibrium basis for scenario comparisons it is necessary to determine the equilibrium conditions of surface and

groundwater systems considering their interactions and the considerable lag times involved in reaching equilibrium.

Figure 1-3 shows an indicative timeline of groundwater use, impact on river, and how this has typically been treated in

river model calibration, and what the actual equilibrium impact on the river would be. By running the groundwater models

until a ‘dynamic equilibrium’ is reached, a reasonable estimate of the ultimate impact on the river of current groundwater

use is obtained. A similar approach is used to determine the ultimate impact of future groundwater use.

Figure 1-3. Timeline of groundwater use and resultant impact on river


1 Introduction

For some groundwater management units – particularly fractured rock aquifers – there is significant groundwater

extraction but no model available for assessment. In these cases there is the potential for considerable impacts on

streamflow. At equilibrium, the volume of water extracted must equal the inflows to the aquifer from diffuse recharge,

lateral flows and flows from overlying rivers. The fraction that comes from the overlying rivers is determined using a

‘connectivity factor’ that is estimated from the difference in levels between the groundwater adjacent to the river and the

river itself, the conductance between the groundwater pump and the river, and the hydrogeological setting. Given the

errors inherent in this method, significant impacts are deemed to be those about 2 GL/year for a subcatchment, which

given typical connectivity factors translates to groundwater extraction rates of around 4 GL/year for a subcatchment.

1.6 Monthly water accounts

Monthly water accounts provide an independent set of the different water balance components by river reach and by

month. The water accounting differs from the river modelling in a number of key aspects:

• the period of accounting extends to 2006 where possible, which is typically more recent than the calibration and

evaluation periods of the river models assessed. This means that a comparison can produce new insights about

the performance and assumptions in the river model, as for example associated with recent water resources

development or the recent drought in parts of the MDB

• the accounting is specifically intended to estimate, as best as possible, historical water balance patterns, and

used observed rather than modelled data wherever possible (including recorded diversions, dam releases and

other operations). This reduces the uncertainty associated with error propagation and assumptions in the river

model that were not necessarily intended to reproduce historical patterns (e.g. differences in actual historical

and potential future degree of entitlement use)

• the accounting uses independent, additional observations and estimates on water balance components not

used before such as actual water use estimates derived from remote sensing observations. This can help to

constrain the water balance with greater certainty.

The water accounting methodology invokes models and indirect estimates of water balance components where direct

measurements are not available. These water accounts are not an absolute point of truth. They provide an estimate of

the degree to which the river water balance is understood and gauged, and a comparison between river model and water

account water balances provides one of several lines of evidence to inform our (inevitably partially subjective)

assessment of model uncertainty and its implications for the confidence in findings. The methods for water accounting

are based on existing methods and those used by Kirby et al. (2006) and Van Dijk et al. (2008) and are described in

detail in Kirby et al. (2008).

1.6.1 Wetland and irrigation water use

An important component of the accounting is an estimate of actual water use based on remote sensing observations.

Spatial time series of monthly net water use from irrigation areas, rivers and wetlands are estimated using interpolated

station observations of rainfall and climate combined with remote sensing observations of surface wetness, greenness

and temperature. Net water use of surface water resources is calculated as the difference between monthly rainfall and

monthly actual evapotranspiration (AET).

AET estimates are based on a combination of two methods. The first method uses surface temperature remotely sensed

by the AVHRR series of satellite instruments for the period 1990 to 2006 and combines this with spatially interpolated

climate variables to estimate AET from the surface energy balance (McVicar and Jupp, 2002). The second method

loosely follows the FAO56 ‘crop factor’ approach and scales interpolated potential evaporation (PET) estimates using

observations of surface greenness and wetness by the MODIS satellite instrument (Van Dijk et al., 2008). The two

methods are constrained using direct on-ground AET measurements at seven study sites and catchment streamflow

observations from more than 200 catchments across Australia. Both methods provide AET estimates at 1 km resolution.


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The spatial estimates of net water use are aggregated for each reach and separately for all areas classified as either

irrigation area or floodplains and wetlands. The following digital data sources were used:

• land use grids for 2000/01 and 2001/02 from the Bureau of Rural Sciences (adl.brs.gov.au/mapserv/landuse/)

• NSW wetlands maps from the NSW Department of Environment and Conservation (NSW DEC)

• hydrography maps, including various types of water bodies and periodically inundated areas, from Geoscience

Australia (GA maps; Topo250K Series 3)

• long-term rainfall and AET grids derived as outlined above

• LANDSAT satellite imagery for the years 1998 to 2004.

The reach-by-reach estimates of net water use from irrigation areas and from floodplains and wetlands are subject to the

following limitations:

• partial validation of the estimates suggested an average accuracy in AET estimation within 15 percent, but

probably decreasing with the area over which estimates are averaged. Uncertainty in spatial estimates

originates from the interpolated climate and rainfall data as well as from the satellite observations and the

method applied

• errors in classification of irrigation and floodplain/wetland areas may have added an unknown uncertainty to the

overall estimates, particularly where subcatchment definition is uncertain or wetland and irrigation areas are

difficult to discern

• estimated net water use cannot be assumed to have been derived from surface water in all cases as vegetation

may also have access to groundwater use, either directly or through groundwater pumping

• estimated net water use can be considered as an estimate of water demand that apparently is met over the

long-term. Storage processes, both in irrigation storages and wetlands, need to be simulated to translate these

estimates in monthly (net) losses from the river main stem.

Therefore, the AET and net water use estimates may be used internally in conceptual water balance models of wetland

and irrigation water use that include a simulated storage.

1.6.2 Calculation and attribution of apparent ungauged gains and losses

In a river reach, ungauged gains or losses are the difference between the sum of gauged main stem and tributary inflows,

and the sum of main stem and distributary outflows and diversions. This would be equal to measured main stem outflows

and water accounting could occur with absolute certainty. The net sum of all gauged gains and losses provides an

estimate of ungauged apparent gains and losses. There may be differences between apparent and real gains and losses

for the following reasons:

• apparent ungauged gains and losses will also include any error in discharge data that may originate from errors

in stage gauging or from the rating curves associated to convert stage height to discharge

• ungauged gains and losses can be compensating and so appear smaller than in reality. This is more likely to

occur at longer time scales. For this reason water accounting was done on a monthly time scale

• changes in water storage in the river reach, connected reservoirs, or wetlands can lead to apparent gains and

losses that become more important as the time scale of analysis decreases. A monthly time scale has been

chosen to reduce storage change effects, but they can still occur.

The monthly pattern of apparent ungauged gains and losses are evaluated for each reach in an attempt to attribute them

to real components of water gain or loss. The following techniques are used in sequence:

• analysis of normal (parametric) and ranked (non-parametric) correlation between apparent ungauged gains and

losses on one hand, and gauged and estimated water balance components on the other hand. Estimated

components included SIMHYD estimates of monthly local inflows and remote sensing-based estimates of

wetland and irrigation net water use

• visual data exploration: assessment of temporal correlations in apparent ungauged gains and losses to assess

trends or storage effects, and a comparison of apparent ungauged gains and losses with a time series of

estimated water balance components.


1 Introduction

Based on the above information, apparent gains and losses are attributed to the most likely process, and an appropriate

method was chosen to estimate the ungauged gain or loss using gauged or estimated data.

The water accounting model includes the following components:

• a conceptual floodplain and wetland running a water balance model that estimates net gains and losses as a

function of remote sensing-based estimates of net water use and main stem discharge observations

• a conceptual irrigation area running a water balance model that estimates (net) total diversions as a function of

any recorded diversions, remote sensing-based estimates of irrigated area and net crop water use, and

estimates of direct evaporation from storages and channels

• a routing model that allows for the effect of temporary water storage in the river system and its associated water

bodies and direct open water evaporation

• a local runoff model that transforms SIMHYD estimates of local runoff to match ungauged gains.

These model components are described in greater detail in Kirby et al. (2008) and are only used where the data or

ancillary information suggests their relevance. Each component has a small number of unconstrained or partially

constrained parameters that need to be estimated. A combination of direct estimation as well as step-wise or

simultaneous automated optimisation is used, with the goal to attribute the largest possible fraction of apparent

ungauged gains and losses. Any large residual losses and gains suggest error in the model or its input data.

1.7 Groundwater modelling

Groundwater assessment, including groundwater recharge modelling, is undertaken to assess the implications of the

climate and development scenarios on groundwater management units (GMUs) across the MDB. A range of methods

are used appropriate to the size and importance of different GMUs. There are over 100 GMUs in the MDB, and the

choice of methods was based on an objective classification of the GMUs as high, medium or low priority.

Rainfall-recharge modelling is undertaken for all GMUs. For dryland areas, daily recharge was assessed using a model

that considered plant physiology, water use and soil physics to determine vertical water flow in the unsaturated zone of

the soil profile at a single location. This model is run at multiple locations across the MDB in considering the range of soil

types and land uses to determine scaling factors for different soil and land use conditions. These scaling factors are used

to scale recharge for given changes in rainfall for all GMUs according to local soil types and land uses.

For many of the higher priority GMUs, recharge is largely from irrigation seepage. In New South Wales this recharge has

been embedded in the groundwater models as a percentage of the applied water. For irrigation recharge, information

was collated for different crop types, irrigation systems and soil types, and has been used for the scenario modelling.

For high priority GMUs numerical groundwater models are being used. In most cases these already exist but often

require improvement. In some cases new models are being developed. Although the groundwater models have seen

less effort invested in their calibration than the existing river models, the project has invested considerable effort in model

calibration and various cross-checks to increase the level of confidence in the groundwater modelling.

For each groundwater model, each scenario is run using river heights as provided from the appropriate river system

model. For recent and future climate scenarios, adjusted recharge values are also used, and for future development the

2030 groundwater extractions levels are used. The models are run for two consecutive 111-year periods (to match the

111-year period used for the river modelling). The average surface-groundwater flux values for the second 111-year

period are passed back to the river models as the equilibrium flux. The model outputs are used to assess indicators of

groundwater use and reliability.

For lower priority GMUs no models are available and the assessments are limited to simple estimates of recharge,

estimates of current and future extraction, allocation based on State data, and estimates of the current and future

impacts of extraction on streamflow where important.


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1.8 Environmental assessment

Environmental assessments on a region by region basis consider the environmental assets already identified by State

governments or the Australian Government that are listed in the Directory of Important Wetlands in Australia

(Environment Australia, 2001) or the updated on-line database of the directory. From this directory, environmental assets

are selected for which there exists sufficient publicly available information on hydrological indicators (such as commence-

to-fill levels) which relate to ecological responses such as bird breeding events.

Information sources include published research papers and reports, accessible unpublished technical reports, or advice

from experts currently conducting research on specific environmental assets. In all cases the source of the information

on the hydrological indicators used in each assessment is cited. The selection of the assets for assessment and

hydrologic indicators was undertaken in consultation with State governments and the Australian Government through

direct discussions and through reviews by the formal internal governance and guidance structures of the project.

The Directory of Important Wetlands in Australia (Environment Australia, 2001) lists over 200 wetlands in the MDB.

Information on hydrological indicators of ecological response adequate for assessing scenario changes only exists for

around one-tenth of these. More comprehensive environmental assessments are beyond the terms of reference for the

project. The Australian Department of Environment, Water, Heritage and the Arts has separately commissioned a

compilation of all available information on the water requirements of wetlands in the MDB that are listed in the Directory

of Important Wetlands in Australia.

For regions where the above selection criteria identify no environmental assets, the river channel itself is considered as

an asset and ecologically-relevant hydrologic assessments are reported for the channel. The locations for which these

assessments are provided are guided by prior studies. In the Victorian regions for example, detailed environmental flow

studies have been undertaken which have identified environmental assets at multiple river locations with associated

hydrological indicators. In these cases a reduced set of locations and indicators has been selected in direct consultation

with the Victorian Department of Sustainability and Environment. In regions where less information is available,

hydrological indicators may be limited to those that report on the water sharing targets that are identified in water

planning policy or legislation.

Because the environmental assessments are a relatively small component of the project, a minimal set of hydrological

indicators are used in assessments. In most cases this minimum set includes change in the average period between

events and change in the maximum period between events as defined by the indicator.

A quality assurance process is applied to the results for the indicators obtained from the river system models which

includes checking the consistency of the results with other river system model results, comparing the results to other

published data and with the asset descriptions, and ensuring that the river system model is providing realistic estimates

of the flows required to evaluate the particular indicators.

1.9 References

Agrecon (2005) Agricultural Reconnaissance Technologies Pty Ltd Hillside Farm Dams Investigation. MDBC Project 04/4677DO.

Australian Bureau of Statistics (2004) Population projections for Statistical Local Areas 2002 to 2022. (ASGC 2001). ABS Catalogue No. 3222.0. Available at: www.abs.gov.au

Battaglia M and Sands P (1997) Modelling site productivity of Eucalyptus globulus in response to climatic and site factors. Australian Journal of Plant Physiology 24, 831–850.

Brown AE, Podger GM, Davidson AJ, Dowling TI and Zhang L (2006) A methodology to predict the impact of changes in forest cover on flow duration curves. CSIRO Land and Water Science Report 8/06. CSIRO, Canberra.

Chiew FHS, Teng J, Kirono D, Frost A, Bathols J, Vaze J, Viney N, Hennessy K and Cai W (2008a) Climate data for hydrologic scenario modelling across the Murray-Darling Basin. A report to the Australian government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia. In prep.

Chiew FHS, Vaze J, Viney N, Jordan P, Perraud J-M, Zhang L, Teng J, Pena J, Morden R, Freebairn A, Austin J, Hill P, Wiesenfeld C and Murphy R (2008b) Rainfall-runoff modelling across the Murray-Darling Basin. A report to the Australian government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia. In prep.

Chiew FHS (2006) An overview of methods for estimating climate change impact on runoff. In: Proceedings of the 30th Hydrology and Water Resources Symposium, December 2006, Launceston.

Chiew FHS and Leahy C (2003) Comparison of evapotranspiration variables in Evapotranspiration Maps of Australia with commonly used evapotranspiration variables. Australian Journal of Water Resources 7, 1–11.


1 Introduction

Chiew FHS, Peel MC and Western AW (2002) Application and testing of the simple rainfall-runoff model SIMHYD. In: Singh VP and Frevert DK (Eds), Mathematical Models of Small Watershed Hydrology and Application. Littleton, Colorado, pp335–367.

DSE (2004) Victoria in Future 2004 – Population projections. Department of Sustainability and Environment, Victoria. Available at: www.dse.vic.gov.au

Environment Australia (2001) A directory of important wetlands in Australia. Third edition. Environment Australia, Canberra. Available at: http://www.environment.gov.au/water/publications/environmental/wetlands/pubs/directory.pdf

Geosciences Australia (2007) Man made hydrology GIS coverage (supplied under licence to CSIRO). Australian Government, Canberra.

IPCC (2007) Climate Change 2007: The Physical Science Basis. Contributions of Working Group 1 to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press.

Jeffrey SJ, Carter JO, Moodie KB and Beswick AR (2001) Using spatial interpolation to construct a comprehensive archive of Australian climate data. Environmental Modelling and Software 16, 309–330.

Kirby J, Mainuddin M, Podger G and Zhang L (2006) Basin water use accounting method with application to the Mekong Basin. In: Sethaputra S and Promma K (eds) Proceedings on the International Symposium on Managing Water Supply for Growing Demand, Bangkok, Thailand, 16–20 October 2006, pp 67–77. Jakarta: UNESCO.

Kirby J et al. (2008) Reach-level water accounting for 1990–2006 across the Murray-Darling Basin. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia. In prep.

Marcar NE, Benyon RG, Polglase PJ, Paul KI, Theiveyanathan S and Zhang L (2006) Predicting the Hydrological Impacts of Bushfire and Climate Change in Forested Catchments of the River Murray Uplands: A Review. CSIRO Water for a Healthy Country.

McVicar TR and Jupp DLB (2002) Using covariates to spatially interpolate moisture availability in the Murray-Darling Basin. Remote Sensing of Environment 79, 199–212.

Nash JE and Sutcliffe JV (1970) River flow forecasting through conceptual models 1: A discussion of principles. Journal of Hydrology 10, 282–290.

Nathan RJ, Jordan PW and Morden R (2005) Assessing the impact of farm dams on streamflows 1: Development of simulation tools. Australian Journal of Water Resources 9, 1–12.

New South Wales Government (2000) Water Management Act 2000 No 92. New South Wales Parliament, December 2000. Available at http://www.dnr.nsw.gov.au/water/wma2000.shtml

Queensland Government (2000) Water Act 2000. Queensland Government, Brisbane.

South Australia Government (2004) Natural Resources Management Act 2004. The South Australian Government Gazette, Adelaide, September 2004. Available at: www.governmentgazette.sa.gov.au

Tan KS, Chiew FHS, Grayson RB, Scanlon PJ and Siriwardena L (2005) Calibration of a daily rainfall-runoff model to estimate high daily flows. MODSIM 2005 International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand, December 2005, pp. 2960–2966. ISBN: 0-9758400-2-9. http://www.mssanz.org.au/modsim05/papers

Van Dirk AIJM et al. (2008) Uncertainty assessments for scenario modelling. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project, CSIRO Australia. In prep.

VicMap (2007) Topographic data series. State of Victoria. Available at http://services.land.vic.gov.au/maps/imf/search/Topo30Front.jsp

Victoria Government (1989) Water Act 1989, Act Number 80/1989. Parliament of Victoria.


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2 Overview of the region

The Goulburn-Broken region is in north-central Victoria and covers 2 percent of the total area of the Murray-Darling Basin

(MDB). The region is based around the Goulburn and Broken Rivers. The population is 144,000 or 7 percent of the MDB

total, concentrated in the centres of Shepparton, Nagambie, Benalla, Kyabram and Tatura. About half the region is

devoted to dryland cereal cropping and grazing and about one-twelfth is irrigated dairy pasture and horticultural cropping.

An extensive irrigated area stretches from south and east of Shepparton to west of Tatura and Kyabram. Approximately

177,600 ha were irrigated in 2000 including 158,800 ha for pastures and hay and 8,600 ha for orchard production. The

lower Goulburn River and floodplain downstream of Loch Gary are listed as nationally important wetlands.

The region generates approximately 11 percent of the runoff within the MDB. The rainfall, runoff and the fraction of

rainfall that becomes runoff in the Goulburn-Broken region, particularly in the southern parts, are amongst the highest in

the MDB. The total annual licensed surface water diversions within the region in 2000 were around 1569 GL/year,

including urban entitlements of 40 GL and diversions to augment water supplies in the Campaspe and Loddon-Avoca

regions. Slightly more than 90 percent of the total diversions for irrigation were sourced from surface water. The region

uses around 14 percent of the surface water diverted for irrigation in the MDB and 5.4 percent of the total groundwater

used in the MDB. Small dams with their own catchment area in the upper part of the region have an estimated storage

capacity of 105 GL.

This chapter summarises the region’s biophysical features including rainfall, topography, land use and the environmental

assets of significance. It outlines the institutional arrangements for the region’s natural resources and presents key

features of the surface and groundwater resources of the region including historical water use.

2.1 The region

The Goulburn-Broken region is entirely located in north-central Victoria and covers 22,378 km2 or 2.1 percent of the MDB.

It is bounded to the east by the Ovens region, to the north by the Murray River, to the west by the Campaspe region and

forms the southern edge of the MDB. The region spans from the foothills of the Great Dividing Range near Alexandra

and Yea in central Victoria to the riverine plains in northern Victoria and the floodplain of the Murray River.

The major water resources in the Goulburn-Broken region include the Goulburn and Broken rivers, fractured rock and

alluvial aquifers and water storages. Both private and public infrastructure is associated with these water resources

including Lake Eildon. The average annual rainfall is 764 mm varying from nearly 1500 mm in the south to 450 mm in the

north. Rainfall can vary considerably from year to year with long periods over several years or decades that are

considerably wetter or drier than others. Despite this variability, the region’s average annual rainfall has remained

relatively consistent over the past 111 years. The average annual rainfall over the past ten years is around 15 percent

lower than the long-term (1895 to 2006) average values (Figure 2-1).


2 Overview

of the region

0

200

400

600

800

1000

1200

1400

1895 1915 1935 1955 1975 1995

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Figure 2-1. 1895–2006 annual and monthly rainfall averaged over the region. The curve on the annual graph shows the low frequency

variability.

The Goulburn-Broken region contributes around 11 percent of the total runoff in the MDB from 2 percent of the total area

of the MDB. The average annual modelled runoff over the region for the 111-year period is 149 mm and mostly occurs in

winter and early spring. The average annual modelled runoff over the ten-year period 1997 to 2006 was 41 percent lower

than the long-term (1895 to 2006) average values. The runoff estimates in the Goulburn-Broken region are relatively

accurate, particularly in the south because there are many gauged catchments from which to estimate the model

parameter values.


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Figure 2-2. Map of dominant land uses of the Goulburn-Broken region with inset showing the region’s location within the

Murray-Darling Basin. The map only shows assets that are assessed in the project (Chapter 7) and that fall within the region. A full list of

key assets associated with the region is in Table 2-2.

The regional population is approximately 144,000 (7 percent of the MDB) and the largest centres are Shepparton,

Benalla, Kyabram and Tatura (Figure 2-2). The dominant land use is dryland agriculture, characterised by broadacre

land uses, primarily cropping and grazing. Land close to the major centres is developed for new and emerging

agricultural commodities and as 'rural living' zones particularly along the Hume Freeway corridor.

Irrigation areas cover much of the northern riverine plains from east of Shepparton to west of Tatura and Kyabram.

Dairying and horticulture are the main irrigated enterprises. There are two main irrigation areas within the

Goulburn-Broken region: the Shepparton Irrigation Area and the Central Goulburn Irrigation Area.


2 Overview

of the region

The Shepparton Irrigation Area covers 81,750 ha of which approximately 50,000 ha is irrigated. The area extends from

about 25 km south of Shepparton to Nathalia and Invergordon in the north. It is bound by the East Goulburn Main

Channel in the east, the Goulburn River in the west and the Broken and Nine Mile Creeks in the north. Some

1500 irrigated holdings are serviced via a network of distribution channels (754 km) and drains (441 km) consisting of

3374 outlets and several thousand structures. High and low reliability water shares (formerly referred to as water right

and sales water respectively) total 181.5 GL. The Central Goulburn Irrigation Area extends south and westwards from

the Goulburn River and covers 173,053 ha of which 113,106 ha is irrigated. It is one of the largest irrigated areas in

Northern Victoria. More than 2800 irrigated holdings are serviced via the extensive network of distribution channels

(1460 km) and drains (882 km). High and low reliability water shares total 385 GL (G-MW, 2007a).

There were around 177,600 ha of irrigated cropping in 2000, predominantly pasture and hay production used for dairy

production. There is a significant area of pome and stone fruits grown in the central area of the region near Shepparton

and small areas of viticulture in the southern areas. The land use area (Table 2-1) is based on the ‘2000 land use of the

MDB grid’, derived from 2001 Bureau of Rural Sciences AgCensus data. Irrigation estimates are based on crop areas

recorded as irrigated in the census.

Table 2-1. Summary of land use in the year 2000 within the Goulburn-Broken region

Land use Area

percent ha

Dryland crops 8.0 178,000

Dryland pasture 50.2 1,121,700

Irrigated crops 7.9 177,600

Cereals 2.8 4,800

Horticulture 1.8 3,200

Orchards 4.8 8,600

Pasture and hay 89.4 158,800

Vine fruits 1.2 2,200

Native vegetation 30.7 685,400

Plantation forests 1.3 29,600

Urban 0.6 13,100

Water 1.3 28,600

Total 100.0 2,234,000

Source: BRS, 2005.

The region is covered by the Goulburn Broken Catchment Management Authority (CMA). The CMA was established in

1997 under the Catchment and Land Protection Act 1994 to achieve effective integration and delivery of land and water

management programs. The Goulburn Broken CMA region includes the Goulburn and Broken river basins.

The Goulburn Broken Regional Catchment Strategy (the Strategy) is the primary integrated planning framework for land,

water and biodiversity management for the period 2003 to 2007 (GBCMA, 2003). It supports several strategies and

action plans and delivers a co-ordinated approach to catchment management to achieve the vision, priorities and

objectives of the community. The Goulburn Broken CMA coordinates and monitors the implementation of the Strategy.

The Strategy takes an assets-based approach to natural resource management and examines how the region’s key

natural resource assets can be enhanced and any threats addressed. The Strategy also identifies the region’s human or

social assets. Water resources, waterways and wetlands are managed to protect high priority water and biodiversity

assets while maintaining sustainable economic use of the region’s water assets.

A river health strategy combines water quality, flow, floodplain, wetland, instream and riparian flora and fauna, waterway,

fisheries and recreation management. It aims to achieve healthy rivers, streams, wetlands, floodplains and adjacent land

that: supports a vibrant range and abundance of natural environments, provides water for human use, sustains the native

flora and fauna, and provides for the community’s social, economic and cultural values. Aspirational targets include:

• maintaining the condition of all reaches (benchmark 2003) of rivers and streams rated as ’good’ or ’excellent’

• improving the overall condition (benchmark 2003) of rivers and streams rated as ’marginal’, ’poor’ and ’very

poor’ by 2050


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• improving and maintaining water quality at optimum levels within and downstream of the catchment for native

ecosystems, recreation, human and animal consumption, agriculture and industry.

The Shepparton Irrigation Region Catchment Strategy, formerly the Shepparton Land and Water Salinity Management

Plan, is a partnership between the local community and all levels of government that provides the framework for land,

water and biodiversity management within the Shepparton Irrigation region. Implementation of the 30-year strategy has

been underway for more than 10 years and covers a wide range of issues including salinity, water quality, biodiversity,

river health, pest plants and animals and climate change (GBCMA, 2007).

2.2 Environmental description

There are five bioregions (DSE, 2007) within the Goulburn-Broken region. There is a small area of the Murray Fans

Bioregion adjacent to the Goulburn River in the north of the region, the Victorian Riverina Bioregion predominates in the

northern area and surrounds small areas of the Northern Inland Slopes Bioregion near Dookie, the Central Victorian

Uplands Bioregion in the southern part and the Highlands Northern Falls Bioregion in the far south of the region.

The Murray Fans Bioregion is characterised by a flat to gently undulating landscape with red brown earths and texture

contrast soils. The vegetation is a mosaic of Plains Grassy Woodland, Pine Box Woodland, Riverina Plains Grassy

Woodland and Riverina Grassy Woodland ecosystems.

The Victorian Riverina Bioregion is characterised by flat to gently undulating landscape on recent unconsolidated

sediments with former stream channels and wide floodplain areas associated with major river systems and prior steams.

Red brown earths and texture contrast soils dominate the riverine plain. The vegetation is predominantly Plains Grassy

Woodland, Plains Grassland, Pine Box Woodland/Riverina Plains Grassy Woodland Mosaic, Riverine Grassy

Woodland/Riverine Sedgy Forest/Wetland Mosaic, Plains Grassy Woodland/Gilgai Plains Woodland/Wetland Mosaic,

Grassy Woodland and Wetland Formation ecosystems (DSE, 2007).

The Northern Inland Slopes Bioregion covers a small area in the north-east and is a mixed complex of both granitic and

metamorphic geology. It consists of foothill slopes and minor ranges that protrude through the surrounding riverine plain.

The Warby Ranges in the north-east are granitic and sedimentary and Mt Major near Dookie is volcanic. The vegetation

is dominated by Grassy Dry Forest, Box Ironbark Forest, Granitic Hills Woodland, Heathy Dry Forest, and Shrubby Dry

Forest ecosystems.

Low-lying corridors of valleys and plains within the Central Victorian Uplands Bioregion are dominated by Plains Grassy

Woodland and Valley Grassy Forest ecosystems on the fertile plains, Grassy Woodland and Floodplain Riparian

Woodland ecosystems on the river courses and Herb-rich Foothill Forest and Shrubby Foothill Forest ecosystems on the

more fertile slopes with outwash. The less fertile hills support Grassy Dry Forest and Heathy Dry Forest ecosystems

(DSE, 2007).

The Highlands Northern Falls Bioregion is the northerly aspect of the Great Dividing Range. These dissected uplands

have moderate to steep slopes, high plateaus and alluvial flats along the main valleys. The vegetation is a mosaic of

Herb-rich Foothill Forest and Shrubby Dry ecosystems that dominate large areas of lower slopes Montane Dry Woodland

and Heathy Dry Forest ecosystems on the upper slopes and plateau and Grassy Dry Forest and Valley Grassy Forest

ecosystems associated with major river valleys (DSE, 2007).

The region was once almost entirely covered in native vegetation – forests in the south and open woodlands in the north.

Native vegetation remains in the mountainous far south on the steepest slopes but the valleys and plains have been

extensively cleared. About 70 percent or 1.7 million ha of native vegetation has been cleared since European settlement.

Bioregions suited to intensive agriculture have been extensively cleared – 97 percent of the Victorian Riverina and

89 percent of the Northern Inland Slopes bioregions. Most threatened species of flora are found in the understorey:

grasses, herbs and low shrubs (GBCMA, 2003).

The wetlands within the region that have national or international importance are detailed in Table 2-2. There are some

very small areas of internationally significant wetlands that extend from the Murray Region – these are discussed in more

detail in the Murray region report (CSIRO, 2008). Wetlands may be regionally important depending on local criteria.

All wetlands are important for a variety of ecological reasons. They may be historically significant or have high cultural

value, particularly to Indigenous people. Part of the lower Goulburn River floodplain is a nationally important wetland


2 Overview

of the region

(VIC052) (Table 2-2). The nominated area covers 13,000 ha downstream of the Goulburn Weir to the Murray River

junction. It consists of a large number of billabongs, anabranches and marginal swamps and includes Gemmill’s Swamp,

Reedy Swamp State Wildlife Refuges, and the Loch Gary Wildlife Management Cooperative Area.

The floodplain receives water from the Goulburn River via Goulburn Weir diversions and via a number of effluent

channels. The vegetation is dominated by River Red Gum (Eucalyptus camaldulensis) forest and woodland and more

limited areas of Grey Box (E. mircocarpa) and Yellow Box (E. melliodora), White Box (E. albens) and Black Box

(E. largiflorens). Other flora includes a range of threatened species. Approximately 34 waterbird species are recorded for

Gemmill’s Swamp. Over 1000 ibis are recorded regularly at Reedy Swamp. Recorded threatened species include

Magpie Geese (Anseranas semipalmata), Bush Thick-knee (Burhinus magnirostris), and Superb Parrot (Polytelis

swainsonii) (Environment Australia, 2001).

The section of the Lower Goulburn River from Loch Gary to the confluence with the Murray River is also a wetland of

national importance. This section (Reach 5) provides habitat for 11 species of native fish: Silver Perch (Bidyanus

bidyanus), River Blackfish (Gadopsis marmoratus), Flat-headed Galaxias (Galaxias rostratus), Western Carp Gudgeon

(Hypseleotris klunzingeri), Trout Cod (Maccullochella macquariensis), Murray Cod (Maccullochella peelii peelii), Golden

Perch (Macquaria ambigua), Murray Rainbowfish (Melanotanenia fluviatilis) Flat-headed Gudgeon (Philypnodon

grandiceps), Australian Smelt (Retropinna semoni) and Freshwater Catfish (Tandanus tandanus). Introduced species

such as Carp (Cyprinus carpio) are also found in this area (Cottingham et al., 2003).

Table 2-2. Ramsar wetlands and wetlands of national significance located within the Goulburn-Broken region

Site Code Directory of Important Wetlands in Australia name Area(1) Ramsar sites(2)

ha

VIC036 Broken Creek # 2,500 none

VIC043 Kanyapella Basin 2,581 none

VIC051 Lower Broken River 1,268 none

VIC052 Lower Goulburn River Floodplain # 13,000 none

VIC053 Muckatah Depression # 2,909 none

VIC060 Wallenjoe Wetlands 303 none

VIC088 Central Highlands Peatlands 33 none

VIC145 Howqua River** 1,520 none

VIC146 Big River 1,875 none (1)Wetland areas have been extracted from the Australian Wetlands Database and are assumed to be correct as provided from State and Territory agencies (2)The Goulburn-Broken region does contain some very small areas of internationally significant wetlands - these are covered in assessments of the Murray Region # also extends into the Murray region ** plus a 200 m buffer on either side of the river in the upper part of the reach which narrows to 20 m of PLWF at the lower part of the reach Source: A Directory of Important Wetlands in Australia (Environment Australia, 2001).

2.3 Surface water resources

2.3.1 Rivers and storages

The Goulburn River flows from its headwaters in the Great Dividing Range south of Alexandra in a north-westerly

direction to Lake Eildon. A number of small tributaries, including the Big River, Jamieson River and Howqua River, flow

into the Eildon reservoir (Lake Eildon) near Eildon. The Goulburn River flows westwards from Lake Eildon to Seymour,

then northwards to Shepparton and finally north-westwards towards Echuca where it joins the Murray River, upstream of

Torrumbarry Weir.

The Broken River flows in a northerly direction from its headwaters south of Benalla in central Victoria. It flows west from

Benalla and joins the Goulburn River at Shepparton. The Broken Creek flows from the catchments north of Benalla


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(including breakaway flood flows from the Broken River) in a north-westerly direction through Numurkah to the Murray

River at Barmah. Part of its length forms the northern boundary of the region.

The Goulburn River is a major supplier of irrigation water to the Goulburn, Broken, Campaspe and Loddon valleys. The

main storage is Lake Eildon which was first constructed in 1915 and enlarged several times. It was completed in 1955

and has a storage capacity of 3334 GL. It was designed to store sufficient water for two dry seasons. Goulburn Weir, first

constructed in 1881 and reconstructed in 1987, has a current storage capacity of 25.5 GL. Waranga Basin has a storage

capacity of 432 GL and the capacity of Greens Lake is 32 GL. Lake Nillahcootie on the Broken River was completed in

1967 and has a capacity of 40.4 GL. The Lake Mokoan storage is being decommissioned with most of the site to be

rehabilitated as a major wetland complex consisting of nine pre-existing wetlands, the largest being Winton Swamp.

The Goulburn River system augments irrigation in the Campaspe and Loddon-Avoca regions. Water stored in Lake

Eildon is diverted at Goulburn Weir near Nagambie into the Cattanach and Stuart Murray canals. The Cattanach Canal

delivers water to Waranga Basin. It is connected to the Loddon and Campaspe rivers by the Waranga Western Channel

(G-MW, 2007b). Waranga water supplements the limited capacity of the Loddon storages and improves water quality (G-

MW, 2007a). Storage capacity of small farm dams with their own catchment used for irrigation and stock and domestic

purposes is estimated at 105 GL (VicMap, 2007).

2.3.2 Surface water management institutional arrangements

Water for consumptive use is taken from water bodies under entitlements issued by Government and authorised under

the Water Act 1989. The Victorian Government retains the overall right to the use, flow and control of all surface water.

The Minister for Water is responsible for allocating bulk entitlements for consumptive use and environmental water

reserves and has allocated responsibilities for the operational management of the Environmental Water Reserve to

catchment management authorities. There is provision for other non-consumptive uses including recreation. Rights are

allocated to private consumers for irrigation and stock and domestic use. Water for consumptive use is allocated to water

authorities by bulk entitlement. They distribute the water to their customers via licence. Many individuals have a right to

take water for domestic and stock use without a licence from a water source such as a catchment dam or groundwater

bore. Water previously available as irrigation sales water was converted into independent entitlement under the Sales

Water Reform Package (DSE, 2007a).

The region’s surface water resources are covered by bulk entitlements for water allocation from the Broken River and the

Goulburn River and its tributaries and for all urban water use (Table 2-3). There are private diverter licences in

unregulated parts of the region. In 2005/06 there was 1958.6 GL of bulk entitlement and 28.9 GL of licenced private

diversion. The MDB cap on surface water diversions is set at 2034 GL for the combined Goulburn and Broken systems.

Formal rights to water for environmental use were established under the Victorian Water (Resources Management) Act

2005. The environmental water reserve for the Goulburn Basin includes 124.6 GL held by the Minister for the

Environment, passing flows released as a condition of consumptive bulk entitlements held by Goulburn-Murray Water

and all other water in the catchment not allocated for consumptive use. No basic rights are quantified in water

management plans. Diversions are allowed under Section 8(1) of the Water Act 1989. There is also harvesting of runoff

into farm dams (DSE, 2006).

Coliban Water, Goulburn Valley Water, North East Water and Goulburn-Murray Water are responsible for the urban

water supply in the Goulburn-Broken region. Goulburn-Murray Water provides Coliban Water and Goulburn Valley Water

with water for towns connected to the Goulburn-Murray irrigation channels and the Waranga channel system (DSE,

2006). Goulburn-Murray Water is also responsible for managing groundwater and surface water licensed diversions from

the Goulburn-Broken catchment. Goulburn-Murray Water operates Lake Eildon, Goulburn Weir, Waranga Basin and

Greens Lake as part of the Goulburn River system and Lake Nillahcootie and Winton Swamp on the Broken River

system. The Goulburn Broken Catchment Management Authority is responsible for waterway management (DSE, 2006).

Traditional water entitlements of water rights (including domestic and stock allowances and take-and-use licences for

regulated water systems managed by Goulburn-Murray Water) were unbundled to create a water share/delivery share in

districts, or extraction share on waterways and a water use licence. A water share is a legally recognised, secure share

of the water available to be taken from a water system.


2 Overview

of the region

The delivery share provides an entitlement to have water delivered to land in an irrigation district and a water use licence

allows irrigators to operate. High and low reliability water shares replaced water rights (DSE, 2008).

Table 2-3. Summary of surface water sharing arrangements

Water products Priority of access Allocated entitlement

GL/y

Basic rights

Stock and domestic rights not stated

Native title none

Extraction shares

Total extraction limit 1973.2

Urban bulk entitlements high 43.8(1)

Industry bulk entitlements high 0

Rural bulk entitlements high and low 1900.4(2)

Unregulated river licences low 28.9(3)

Environmental provisions

Total environmental share Not stated

Environmental entitlement low 124.6

Additional environmental passing flows

high 134.0

Source: Department of Sustainability and Environment (DSE), 2006. (1) Urban bulk entitlements: sum of bulk entitlements to Coliban Water and Goulburn Valley Water. In addition. Goulburn-Murray Water is required to supply a number of urban centres from its channel system within the Goulburn Valley. (2) Maximum 10 year average diversion in Goulburn-Murray Water bulk entitlement. (3) Unregulated river licences: Sum of individual licences including irrigation farm dams

2.3.3 Water products and use

Surface water diversions and groundwater extractions increased as irrigated crop production grew from the early 1960s.

Annual use (Figure 2-3) is influenced strongly by the availability of low reliability water allocations (prior to unbundling this

was referred to as ‘sales’ water). Most diversions occur within the Shepparton and Central Goulburn irrigation areas for

dairy industry pasture and hay production. The relatively low annual diversion volumes recorded in recent years reflect

the drought conditions experienced.. Annual urban water use is around 40 GL.


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0

500

1000

1500

2000

2500

1980 1985 1990 1995 2000 2005A

nn

ual d

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GL

)

Figure 2-3. Historical surface water diversions from the Goulburn and Broken river catchments

Note: The data in different years are not always fully comparable because the areas defined in each catchment changed, as did the definitions of water uses. Even where data sets should refer to the same records, data from state and Murray-Darling Basin Commission databases often vary. Sources: MDBC, 2007a

2.4 Groundwater

2.4.1 Groundwater management units – the hydrogeology and connectivity

Fractured rock aquifers dominate the region’s highlands. Local groundwater flow systems occur in areas with greater

relief and steeper slopes and respond rapidly to seasonal variations in rainfall. Intermediate groundwater flow systems

operate where there is greater weathering and lower relief. Groundwater quality is good due to rapid recharge and higher

rainfall but yields are relatively low.

More reliable groundwater supplies occur within the alluvial sediments deposited by rivers flowing north from the

highlands. The Renmark Group and Calivil Formation are the deepest sedimentary aquifers in the region and comprise

fluvial clays, silts, sands and gravels that are often hydraulically connected. The sediments are thickest in palaeo-valleys

extending north from the highlands and are referred to as ’deep leads’. The deep leads broaden towards the north and

form a continuous sheet under much of the south-eastern MDB. Coarse sands and gravels allow hydraulic conductivities

as high as 200 m/day. Salinities in the Renmark Group and Calivil Formation are fresher than the overlying aquifer

system, ranging from 300 to 2000 mg/L Total Dissolved Salts (TDS) to as high as 7000 mg/L TDS in some areas.

The Shepparton Formation is the uppermost aquifer system in the alluvial sequence and comprises fluvio-lacustrine silts,

sands and clays. Hydraulic conductivities are 30 m/day in the coarsest units but significantly lower in finer grained

sediments and may promote downward leakage into the underlying the Renmark Group and Calivil Formation.

Carbon-14 dating indicates rainfall recharge occurs across the region and vertical flow is dominant (Cartwright and

Weaver, 2005). Groundwater salinity ranges from 1,000 mg/L TDS to more than 20,000 mg/L TDS.

The aquifers within the region are divided into a number of groundwater management units (GMUs) which are three-

dimensional in nature, allowing for the layered nature of geological formations at different depths. The GMUs relevant to

the region are:

• Alexandra Groundwater Management Area (V11)

• Kinglake Groundwater Management Area (V12)

• Goorombat Groundwater Management Area (V38)

• Nagambie Groundwater Management Area (V41)

• parts of Kialla Groundwater Management Area (V40)

• Shepparton Water Supply Protection Area (V43)

• Campaspe Deep Lead Water Supply Protection Area (V42)

• Katunga Water Supply Protection Area (V39).


2 Overview

of the region

For ease of reference, the various Groundwater Management Areas (GMA) and Water Supply Protection Areas (WSPA)

are simply referred to as GMUs. Where the term WSPA occurs in this report, it refers to regulatory matters not the

groundwater assessment. Only the first six GMUs are assessed in this report. The Campaspe Deep Lead and Katunga

GMUs are mostly located within adjacent catchments and so are not reported here. The GMUs do not cover the entire

region, and those areas not covered are referred to as ‘unincorporated areas’. GMUs within the Goulburn-Broken region

are shown in Figure 2-4.

Approximately 80 percent of the Shepparton GMU is located within the Goulburn-Broken region and the remaining

20 percent is in the Campaspe and Loddon-Avoca regions. Extraction from the Shepparton GMU in the two adjacent

regions are reported here to keep it as a complete entity. The Kinglake GMU covers approximately 92 km2 and straddles

the watershed divide of the Goulburn and Port Phillip catchments. Approximately 78 percent of the GMU is located within

the Goulburn-Broken region.

Part of the Kinglake GMU is situated within fractured rock aquifers and the Alexandra GMU includes the alluvial aquifers

of the upper Goulburn River floodplain. These GMUs are assessed as low to very low priority in the context of the project

on the basis of the size of the aquifers, the level of development and the assumed degree of connectivity with the surface

water system. The remaining GMUs relate to surface sediments and to deep lead and buried aquifers. Management

within the Shepparton GMU is designed to protect the region’s agricultural and natural resources from salinity by regular

pumping of groundwater to provide salinity control. This GMU covers all aquifers contained to a depth of 25 m. The

underlying GMUs associated with the Deep Leads are the Nagambie and Kialla GMUs. Portions of the Campaspe Deep

Lead and Katunga GMUs are located within the Goulburn-Broken region but are reported elsewhere. Available

groundwater extraction, entitlement and recharge data are itemised for each GMU in the region in Table 2-4.


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Figure 2-4. Map of groundwater management units within the Goulburn-Broken region


2 Overview

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Table 2-4. Categorisation of groundwater management units, including annual extraction, entitlement and recharge details

Code GMU name Priority Total entitlement

Current extraction (2004/05)

Permissible consumptive

volume

Recharge(4)

GL/y

V11 Alexandra GMA low 1.71 0.70 1.9 1.9

V12 Kinglake GMA(1) very low 1.49 1.05 3.8 4.4

V38 Goorambat GMA very low 1.54 0.48 4.9 2.6

V40 Kialla GMA low 2.33 0.86 2.8 23

V41 Nagambie GMA low 6.65 4.55 5.7 8.5

V43 Shepparton WSPA(2) medium 203.6 80.65 none set 268

- Unincorporated Areas(3) - 7.87 3.90 none set 239

Note: Current extraction volumes have been supplied by DSE, and include estimates of stock and domestic use of 0.10, 0.53, 0.03, 0.05, 0.14, 0.83 and 0.36 GL/y for Alexandra, Kinglake, Goorambat, Kialla, Nagambie and Shepparton GMUs and unincorporated areas. (1) Approximately 78% of the Kinglake GMU falls within the Goulburn Basin. Groundwater entitlements and use are for this portion of the GMU only as the remainder lies outside the MDB. (2) Approximately 80% of the Shepparton GMU is contained within the Goulburn-Broken reporting region. Entitlement and extraction values are reported for the whole GMU. (3) Figures for the unincorporated areas relate to areas of fair groundwater quality (< 1500 mg/L TDS) in the upper part of the catchment. (4) Includes only rainfall recharge in non-modelled areas and all forms of recharge in modelled areas.

2.4.2 Water management institutional arrangements

Goulburn-Murray Water is responsible for groundwater licensing within the region. Permissible Annual Volumes (PAVs)

for groundwater were best estimates of the available resource during the 1990s. PAVs have been superseded by

Permissible Consumptive Volumes (PCVs) that are issued through Ministerial Order. Ongoing hydrogeological

investigations provide information that informs the development of PCVs. The Shepparton Irrigation Region was declared

a WSPA in 1995. A PCV has not been set as management of the resource is aimed at salinity control. Monitoring

identifies risk areas. State legislation broadly controls groundwater extraction within the remainder of the catchment area

and there are provisions that allow for declaration of WSPAs and implementation of groundwater management plans

where there is a threat from increasing rates of groundwater extraction. A WSPA can be declared under the Water Act

1989 to protect the area’s groundwater or surface water resources through the development of a management plan

which aims for equitable management and long-term sustainability (DSE, 2006). Groundwater management plans are

summarised in Table 2-5.

Table 2-5. Summary of groundwater management plans

Description Shepparton WSPA*

Year of plan 1999

Environmental provisions

Planned share Investigated in the development of the plan

Supplementary provisions Investigated in the development of the plan

Adaptive provisions Investigated in the development of the plan

Basic rights

Domestic and stock rights 0.83 GL/y

Native title none

Access licences

Urban none

Planned share 203.6 GL/y (the plan does not differentiate between urban, irrigation or commercial entitlements)

Announced allocation

* Approximately 80% of the Shepparton WSPA is contained within the Goulburn-Broken region.


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2.4.3 Water products and use

Groundwater extraction accounts for 5.4 percent of the MDB total. Extraction for irrigation in the early 1970s was

negligible. Demand increased dramatically after the 1982/83 drought. Groundwater use was encouraged in the 1990s

and charges were waived between 1992 and 1999. A moratorium on new licences was introduced in 1998. Extraction

continued to increase to 2002/03 but then fell slightly in 2004/05 and was estimated at 92.2 GL (including stock and

domestic use of 2.04 GL). Most of the groundwater used in the Shepparton GMU is for dairy pasture production. The

remainder supplements water supplies for horticulture, grain crops, lucerne and vegetables.

Table 2-6. Annual groundwater extraction within the Goulburn-Broken region

Annual groundwater extraction volumes from GMUs

Alexandra GMU Goorambat GMU Kialla GMU (Zone 1 + 2)

Kinglake GMU* Nagambie GMU Shepparton GMU*

Year GL/y

1999/0 NA NA NA NA NA NA

2000/1** 0.7 0.7 1.4 0.9 1.4 128.0


2002/3** 1.2 1.1 2.5 1.6 2.4 120.0


2004/5*** 0.7 0.48 0.86 1.05* 4.55 80.65

Figures do not include stock and domestic use. * Extraction within this GMU incorporates all reported extractions within the GMU. ** Sourced from MDBC (2007b). *** Sourced from DSE (2006). NA – not available

2.5 References

BRS (2005) 1993, 1996, 1998 and 2000 Land Use of the Murray-Darling Basin, Version 2. Resource Identifier: ID01. Online digital dataset and spatial data layer. File identifier: http://adl.brs.gov.au/findit/metadata_files/a_mdblur9abl_00711a00.xml Product access: http://data.brs.gov.au/anrdl/a_mdblur9abl_00711a00.xml

Cartwright, I and Weaver, T (2005) Hydrogeochemistry of the Goulburn Valley Region of the Murray Basin, Australia: implications for flow paths and resource vulnerability. Hydrogeology Journal, v13, p 752-770.

Cottingham P, Crook D, Hillman T, Roberts J, Rutherford I and Stewardson M (2003) Flow-related environmental issues associated with the Gouburn River below Lake Eildon. A report to the Department of Sustainability and Environment, Victoria and the Murray-Darling Basin Commission. CRC for Freshwater Ecology and CRC for Catchment Hydrology. March 2003.

CSIRO (2008) Water Availability in the Murray. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia. In prep.

DSE (2006) State Water Report 2004/05. A statement of Victorian water resources. Department of Sustainability and Environment, Melbourne, June 2006.Available at: http://www.dpi.vic.gov.au/dse/

DSE (2007) State Water Report 2005/06 – a statement of Victorian Water Resources. Department of Sustainability and Environment, Victoria, East Melbourne.

DSE (2007a) Sales Water Reform Package Website. Department of Sustainability and Environment, Melbourne. Available at: http://www.dpi.vic.gov.au/DSE/wcmn202.nsf/LinkView/D3C115F9997B7295CA256FE1001C7DDC59F77945A025B123CA256FDD00136E2D

DSE (2008) Unbundling Reforms www.dse.vic.gov.au/DSE/

Environment Australia (2001) A directory of important wetlands in Australia. Third edition. Environment Australia, Canberra. Available at: http://www.environment.gov.au/water/publications/environmental/wetlands/pubs/directory.pdf

GBCMA (2003) Goulburn Broken Regional Catchment Strategy 2003-2007. Goulburn Broken Catchment Management Authority www.gbcma.vic.gov.au

GBCMA (2007) Shepparton Irrigation Region Catchment Strategy. Goulburn Broken Catchment Management Authority. Available at: www.gbcma.vic.gov.au

G-MW (2007b) Goulburn-Murray Water Irrigation Area Profiles. Goulburn-Murray Water, Tatura, Victoria. Available at http://www.g-mwater.com.au/

G-MW (2007a) Goulburn-Murray Water Storage Levels – online reports. Goulburn-Murray Water, Tatura, Victoria. Available at http://www.g-mwater.com.au/water-resources/storage-levels


2 Overview

of the region

MDBC (2007a) Water Audit Monitoring Reports (1995 to 2004). Nine reports cover the years 1994/5 to 2003/4. Murray-Darling Basin Commission, Canberra. Available at: www.mdbc.gov.au/naturalresources/the_cap/the_WAM_report.htm

MDBC (2007b) Updated summary of estimated impact of groundwater extraction on stream flow in the Murray-Darling Basin. Draft Report. Prepared by REM on behalf of MDBC Canberra.

VicMap (2007) Topographic data series. State of Victoria. Available at http://services.land.vic.gov.au/maps/imf/search/Topo30Front.jsp


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3 Rainfall-runoff modelling This chapter includes information on the climate and rainfall-runoff modelling for the Goulburn-Broken region. It has four sections:

• a summary • an overview of the regional modelling approach • a presentation and description of results • a discussion of key findings.

3.1 Summary

3.1.1 Issues and observations

• The methods used for climate scenario and rainfall-runoff modelling across the Murray-Darling Basin (MDB) are described in Chapter 1. There are no significant differences in the methods used to model the different regions.

3.1.2 Key messages

• The annual rainfall and modelled runoff averaged over the region are 764 mm and 149 mm respectively. Rainfall is generally higher in the winter half of the year and most of the runoff occurs in winter and early spring. Rainfall, runoff and the fraction of rainfall that becomes runoff, particularly in the southern parts, are amongst the highest in the MDB. The region covers 2.1 percent of the MDB area and contributes about 11 percent of the total runoff in the MDB.

• The average annual rainfall and runoff over the ten-year period 1997 to 2006 are 15 percent and 41 percent lower respectively than the long-term (1895 to 2006) average values. The 1997 to 2006 rainfall is statistically different to the 1895 to 1996 average values at a significance level of α = 0.05 and the 1997 to 2006 runoff is statistically different to the 1895 to 1996 average values at a significance level of α = 0.01.

• Rainfall-runoff modelling with climate change projections from global climate models (GCMs) indicates that future runoff in the region will decrease significantly. All the modelling results using climate projections from different GCMs show a decrease in runoff. Under the best estimate (median) 2030 climate average annual runoff would be reduced by 13 percent. The extreme estimate ranges from a 44 to a 2 percent reduction in average annual runoff.

• Projected growth in commercial forestry plantations is negligible. The total farm dam storage volume is projected to increase by 8740 ML or 8 percent by ~2030. This would reduce average annual runoff by about 0.5 percent. The best estimate of the combined impact of climate change and farm dam development is a 14 percent reduction in average annual runoff. Extreme estimates range from a 44 to a 3 percent reduction.

3.1.3 Uncertainty

• Scenario A – historical climate and current development The runoff estimates for the region are relatively accurate because there are many gauged catchments in the region from which to estimate the model parameter values. The observed monthly runoff series and the daily flow duration characteristics at these gauged catchments were reproduced well in the rainfall-runoff model calibration. Rainfall-runoff model verification analyses for the MDB indicate that the mean annual runoff estimated for individual ungauged catchments (using optimised parameter values from a nearby catchment) have an error of less than 20 percent in more than half the catchments and less than 50 percent in almost all the catchments.

• Scenario B – recent climate and current development Scenario B was modelled because the 1997 to 2006 rainfall and runoff are significantly different to the (1895 to


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ainfall-runoffmodelling

2006) long-term means. There is large uncertainty in the Scenario B results because it is based on only ten years of data. The rainfall-runoff modelling uses 100 stochastic replicates of climate inputs based on 1997 to 2006 climate. Scenario B is defined as the replicate that produced the 1997 to 2006 mean annual runoff. This is used to obtain the catchment inflows for the river system modelling.

• Scenario C – future climate and current development The biggest uncertainty in Scenario C modelling is in the global warming projections and the modelled implications of global warming on local rainfall. The uncertainty in the rainfall-runoff modelling of climate change impact on runoff is small compared to the climate change projections. This project accounts for the current uncertainty in climate change projections explicitly by considering results from 15 global climate models and three global warming scenarios based on the Intergovernmental Panel on Climate Change Fourth Assessment report (IPCC, 2007). The results are presented as a best estimate of climate change impact on runoff and as a range of extreme estimates.

• Scenario D – future climate and future development The next biggest uncertainty is in the projections of future increases in commercial forestry plantations and farm dam development and the impact of these developments on runoff. The impact of commercial forestry plantations on runoff is not modelled because the Bureau of Rural Sciences projections indicate negligible growth (BRS, 2005). Farm dam projections use current policy controls in Victoria that limit further farm dam development to stock and domestic dams and an assumption that growth in stock and domestic dam storage will be proportional to the rate of rural population growth. There is uncertainty both as to how landholders will respond to these policies and how governments may set policies in the future.

3.2 Modelling approach

3.2.1 Rainfall-runoff modelling – general approach

The rainfall-runoff modelling approach is described in Chapter 1 and there is more detail in Chiew et al. (2008). A brief summary is given below.

The lumped conceptual daily rainfall-runoff model SIMHYD is used with a Muskingum routing method to estimate daily runoff at 0.05o grids (~ 5 km x 5 km) across the entire MDB for the four climate and development scenarios. The rainfall-runoff model is calibrated against 1975 to 2006 streamflow data from about 180 small and medium size unregulated MDB catchments (50 to 2000 km2). The six parameters of SIMHYD are optimised in the model calibration to maximise an objective function that incorporates the Nash-Sutcliffe efficiency of monthly runoff and daily flow duration curve. Calibration includes a constraint to ensure that the total modelled runoff over the calibration period is within 5 percent of the total recorded runoff. The runoff for a 0.05o grid cell in an ungauged subcatchment is modelled using optimised parameter values for a calibration catchment closest to that subcatchment. The rainfall-runoff model SIMHYD is used because it is simple, has relatively few parameters and provides a consistent basis (that is automated and reproducible) for modelling historical runoff across the entire MDB and assessing the potential impacts of climate change and development scenarios on future runoff. In data-rich areas, specific calibration of SIMHYD or more complex rainfall-runoff models based on expert judgement and local knowledge (as done by some state agencies) may lead to better model calibration for the specific modelling objectives of the area.

3.2.2 Rainfall-runoff modelling for the Goulburn-Broken region

The rainfall-runoff modelling estimates runoff in 0.05o grid cells in 24 subcatchments as defined for the river system modelling in Chapter 4 (Figure 3-1). Optimised parameter values from 14 calibration catchments are used. The impact of commercial forestry plantations on runoff is not modelled because the Bureau of Rural Sciences projections that take into account industry information indicate negligible future growth. Future development of farm dams in Victoria is mainly limited to stock and domestic purposes (Victoria Government, 1989).

The projected increase in farm dams in each subcatchment in the region is estimated by multiplying the projected increase in rural population (DSE, 2004) by the current average storage volume of stock and domestic farm dams (estimated from VicMap 1:25,000 scale topographic mapping) per person in the subcatchment.


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The 2030 projected increases in farm dam storage volume for each subcatchment is given in Appendix A. The rural population is projected to increase by about 24 percent by ~2030. The existing volume of farm dams (irrigation and stock and domestic) is about 105 GL. The total increase in farm dam storage volume by ~2030 is 8.7 GL or 8 percent of the existing total volume.

Figure 3-1. Map of the modelling subcatchments and calibration catchments

3.2.3 Model calibration

Figure 3-2 compares the modelled and observed monthly runoff and daily flow duration curves for the 14 calibration catchments. The calibration results are amongst the most accurate in the MDB. The Nash-Sutcliffe E values for monthly runoff and daily flow duration characteristics are generally greater than 0.8. The volumetric constraint used in the model calibration also ensures that the total modelled runoff is within 5 percent of the total observed runoff.

The calibration to optimise Nash-Sutcliffe E means that more importance is placed on the simulation of high runoff. Therefore SIMHYD modelling of the medium and high runoff are considerably better than the simulation of low runoff. Nevertheless, an optimisation to reduce overall error variance can result in some underestimation of high runoff and overestimation of low runoff.


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This is evident in some of the plots comparing the modelled and observed monthly runoff and the daily flow duration curves. The difference is accentuated in the daily flow duration curves because of the linear scale on the y-axis and normal probability scale on the x-axis. The disagreement between the modelled and observed daily runoff is generally only discernable for runoff that is exceeded less than 0.1 or 1 percent of the time.

The runoff estimates for the region are relatively accurate because there are many calibration catchments from which to estimate the parameter values. The observed monthly runoff and the daily flow duration curves at these catchments were reproduced well in the model calibration. The rainfall-runoff model verification analyses for the MDB indicated that the mean annual runoff for ungauged catchments was under or over estimated by less than 20 percent in more than half the catchments and by less than 50 percent in almost all the catchments when using optimised parameter values from a nearby catchment.


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Figure 3-2. Modelled and observed monthly runoff and daily flow duration curve for the calibration catchments


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3.3 Modelling results

3.3.1 Scenario A – historical climate and current development

Figure 3-3 shows the spatial distribution of mean annual rainfall and modelled runoff for 1895 to 2006 across the region, Figure 3-4 shows the 1895 to 2006 annual rainfall and modelled runoff series averaged over the region, and Figure 3-5 shows the mean monthly rainfall and runoff averaged over the region for 1895 to 2006.

The mean annual rainfall and modelled runoff averaged over the region are 764 mm and 149 mm respectively. The mean annual rainfall varies from about 1500 mm in the south to 450 mm in the north. The modelled mean annual runoff varies from more than 400 mm in the south to 15 mm in the north. Rainfall is higher in the winter half of the year and most of the runoff occurs in winter and spring. The rainfall, runoff and the fraction of rainfall that becomes runoff, particularly in the southern parts, are amongst the highest in the MDB. The region covers 2.1 percent of the MDB area and contributes about 11 percent of the total runoff.

Rainfall and runoff can vary considerably from year to year with long periods over several years or decades that are considerably wetter or drier than others. The coefficients of variation of annual rainfall and runoff averaged over the region are 0.22 and 0.52 respectively and amongst the least variable in the MDB. The tenth percentile, median and ninetieth percentile values across the 18 MDB regions are 0.22, 0.26 and 0.36 respectively for rainfall and 0.54, 0.75 and 1.19 for runoff.

The mean annual rainfall and modelled runoff over the ten-year period 1997 to 2006 are 15 percent and 41 percent lower respectively than the long-term (1895 to 2006) mean values. The 1997 to 2006 rainfall is statistically different to the 1895 to 1996 rainfall at a significance level of α = 0.05 and the 1997 to 2006 runoff is statistically different to the 1895 to 1996 runoff at a significance level of α = 0.01 (with the Student-t and Rank-Sum tests). Scenario B modelling is done because of this significance. Scenario B is a stochastic replicate selected so that its 1895 to 1996 mean annual runoff matches the 1997 to 2006 mean annual runoff. Potter et al. (2008) present a more detailed analysis of recent rainfall and runoff across the MDB.

Figure 3-3. Spatial distribution of mean annual rainfall and modelled runoff averaged over 1895–2006


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3.3.2 Scenario C – future climate and current development

Figure 3-6 shows the percentage change in the modelled mean annual runoff averaged over the Loddon-Avoca, Campaspe and Goulburn-Broken regions under Scenario C relative to Scenario A for the 45 scenarios (15 GCMs for each of the high, medium and low global warming scenarios). The percentage change in the mean annual runoff and rainfall from the corresponding GCMs is also tabulated in Table 3-1. The Loddon-Avoca, Campaspe and Goulburn-Broken regions are aggregated in this way because the river model for this area – the Goulburn Simulation Model (Chapter 4) – covers all three regions. The choice of scenarios for the river system modelling (and linked groundwater modelling) is thus based on the rainfall-runoff modelling results for the three combined regions, rather than on rainfall-runoff modelling results for each region separately.

The plot and table indicate that climate change would significantly reduce runoff across the Loddon-Avoca, Campaspe and Goulburn-Broken regions. All the modelling results show a decrease in runoff. Rainfall-runoff modelling for the high global warming scenario with climate change projections from 60 percent of the GCMs indicated a decrease in mean annual runoff greater than 10 percent. The biggest increase and decrease in runoff come from the high global warming scenario because of the large variation between GCM simulations and the method used to obtain the climate change scenarios (Section 1.3.3). Only results from an extreme ‘dry’, ‘mid’ and extreme ‘wet’ variant are shown (referred to as scenarios Cdry, Cmid and Cwet in subsequent reporting). Results from the second highest reduction in mean annual runoff from the high global warming scenario are used for Scenario Cdry. Results from the second highest increase (or second least decrease) in mean annual runoff from the high global warming scenario are used for Scenario Cwet. The best estimate mean annual runoff results from the medium global warming scenario are used for Scenario Cmid. These are shown in bold in Table 3-1. Scenarios Cdry, Cmid and Cwet indicated a -44, -13 and -2 percent change in mean annual runoff.


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The range (second highest to second lowest) based on the low global warming scenario is -14 to -1 percent change in mean annual runoff. Figure 3-7 shows the mean annual runoff across the region for Scenario A and under Scenarios Cdry, Cmid and Cwet.

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Table 3-1. Summary results under the 45 Scenario C simulations (numbers show percentage change in mean annual rainfall and runoff for Scenario C relative to Scenario A) for the Loddon-Avoca, Campaspe and Goulburn-Broken regions

High global warming Medium global warming Low global warming GCM Rainfall Runoff GCM Rainfall Runoff GCM Rainfall Runoff giss_aom -22 -51 giss_aom -14 -35 giss_aom -6 -16cnrm -18 -44 cnrm -11 -30 cnrm -5 -14ipsl -19 -40 ipsl -12 -27 ipsl -5 -13miroc -7 -28 miroc -5 -19 miroc -2 -9gfdl -11 -26 gfdl -7 -18 gfdl -3 -8csiro -10 -26 csiro -6 -17 csiro -3 -8inmcm -6 -21 mri -5 -14 mri -2 -6mri -7 -20 inmcm -4 -14 inmcm -2 -6mpi -6 -15 mpi -4 -11 mpi -2 -5ncar_ccsm 0 -8 ncar_ccsm 0 -5 ncar_ccsm 0 -2miub -1 -7 miub -1 -5 miub 0 -2iap -3 -6 iap -2 -4 iap -1 -2cccma_t47 -1 -5 cccma_t47 -1 -3 cccma_t47 0 -1cccma_t63 1 -2 cccma_t63 0 -1 cccma_t63 0 -1ncar_pcm 2 -1 ncar_pcm 1 -1 ncar_pcm 1 0


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3.3.3 Summary results for all modelling scenarios

Table 3-2 shows the mean annual rainfall, modelled runoff and actual evapotranspiration under Scenario A (averaged over the region), and the percentage changes in the rainfall, runoff and actual evapotranspiration under scenarios C and D relative to Scenario A. Figure 3-8 shows the mean monthly rainfall and modelled runoff under scenarios A, C and D averaged over 1895 to 2006 for the region. Figure 3-9 shows the daily rainfall and flow duration curves for scenarios A, C and D averaged over the region. The modelling results for all the subcatchments in the region are summarised in Appendix A.

The Cmid (or Cdry or Cwet) results are from rainfall-runoff modelling using climate change projections from one GCM. The comparison of monthly and daily results under Scenario Cmid relative to Scenario A in Figure 3-8 and Figure 3-9 should be interpreted cautiously as the Cmid variant is chosen based on mean annual runoff (Section 3.3.2). However, the C range results shown in Figure 3-8 are based on the second driest and second wettest results for each month separately from the high global warming scenario. The C range results shown in Figure 3-9 are based on the second lowest and second highest daily rainfall and runoff results at each of the rainfall and runoff percentiles from the high global warming scenario. The lower and upper limits of C range are therefore not the same as scenarios Cdry and Cwet reported elsewhere and used in the river system and groundwater models.

Figure 3-8 indicates that the GCM projections show a bigger decrease in the winter half rainfall compared to summer half rainfall and this translates to an even bigger percentage runoff reduction in the winter half when most of the runoff in the region occurs. About two-thirds of the GCMs indicate that the extreme rainfall that is exceeded 0.1 percent of the time will be more intense (Figure 3-9), although all the GCMs show a reduction in mean annual rainfall.

The mean annual runoff over the ten-year period 1997 to 2006 is 41 percent lower than the long-term (1895 to 2006) mean values. Accordingly, 100 replicates of 112-year daily climate sequences are generated for Scenario B modelling, using the annual rainfall characteristics over 1997 to 2006. The replicate that reproduced the 1997 to 2006 mean annual runoff is used to obtain the catchment inflows for the river system modelling in Chapter 4. The change in rainfall has little meaning and is therefore not shown in Table 3-2, because the replicate is chosen based on mean annual runoff.

The modelling results indicate a best estimate of -13 percent change in mean annual runoff by ~2030 (Scenario Cmid). However, there is considerable uncertainty in the climate change impact estimate. Extreme estimates range from -44 to -2 percent change in mean annual runoff. These values are very similar to but not the same as the values in Section 3.3.2 because the values in Section 3.3.2 show results for the combined Loddon-Avoca, Campaspe and Goulburn-Broken regions.

The projected growth in commercial forestry plantations is negligible. The total farm dam storage volume is projected to increase by 8.7 GL by ~2030. The best estimate of the combined impact of climate change and farm dam development is a 14 percent reduction in mean annual runoff. Extreme estimates range from -44 to -3 percent (Scenario D).

Table 3-2. Water balance over the entire region by scenario

Scenario Rainfall Runoff Evapotranspiration mm A 764 149 614 percent change from Scenario A B – -41% – Cdry -19% -44% -12% Cmid -4% -13% -2% Cwet 0% -2% 0% Ddry -19% -44% -12% Dmid -4% -14% -1% Dwet 0% -3% 1%


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scenarios Cdry and Cwet)

Figure 3-9. Daily flow duration curves under scenarios A, C and D averaged over the region (C range is based on the consideration of each rainfall and runoff percentile separately – the lower and upper limits in C range are therefore not the same

as scenarios Cdry and Cwet)

3.4 Discussion of key findings

The mean annual rainfall and modelled runoff averaged over the region are 764 mm and 149 mm respectively. The mean annual rainfall varies from about 1500 mm in the south to 450 mm in the north. The modelled mean annual runoff varies from more than 400 mm in the south to 15 mm in the north. Rainfall is higher in the winter half of the year and most of the runoff occurs in winter and spring. The rainfall, runoff and the fraction of rainfall that becomes runoff, particularly in the southern parts, are amongst the highest in the MDB. The region covers 2.1 percent of the MDB area and contributes about 11 percent of the total runoff in the MDB. The mean annual rainfall and modelled runoff over the ten-year period 1997 to 2006 are 15 percent and 41 percent lower respectively than the long-term (1895 to 2006) mean values. The 1997 to 2006 rainfall is statistically different to the 1895 to 1996 rainfall at a significance level of α = 0.05 and the 1997 to 2006 runoff is statistically different to the 1895 to 1996 runoff at a significance level of α = 0.01 (with the Student-t and Rank-Sum tests).

Although the rainfall over the ten-year period 1997 to 2006 is 15 percent lower than the long-term (1895 to 2006) mean values, the runoff is 41 percent lower than the long-term (1895 to 2006) mean values. The likely reasons for this include: rainfall-runoff is a nonlinear process and the changes in rainfall are amplified more in runoff in a drier climate; subsurface water storage is low after a long dry period and a significant amount of rainfall is required to fill the storage before runoff can occur; and changes in the daily and seasonal rainfall distribution and sequencing of rainfall events could amplify the reduction in runoff (particularly the observed reduction in autumn and winter rainfall – see Potter et al. (2008)).


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The mean annual runoff over the past ten years is similar to the projected decrease in mean annual runoff in the dry 2030 climate extreme. However, it is not sufficient evidence that the hydroclimate has shifted to a new regime because it is based on only ten years of data. If the hydroclimate has shifted to a new regime (like the dry 2030 climate extreme), the dry conditions over the past ten years will occur more frequently.

The runoff estimates for the region are relatively accurate because there are many calibration catchments in the region from which to estimate the parameter values. The observed monthly runoff series and the daily flow duration characteristic at these calibration catchments were reproduced well in the SIMHYD calibration.

Rainfall-runoff modelling with climate change projections from global climate models indicates that future runoff will decrease significantly. All the modelling results using climate change projections from different global climate models showing a decrease in runoff. Most of the global climate models show a greater reduction in winter half rainfall and this translates to an even bigger percent reduction in winter half runoff, when most of the runoff in the region occurs. However, although the projections indicate a decrease in mean annual rainfall and runoff, two-thirds of the results also indicate that the extreme rainfall events will be more intense.

The best estimate 2030 climate would be a 13 percent reduction in mean annual runoff. However, there is considerable uncertainty in the modelling results and the extreme estimates range from a -44 to a -2 percent change in mean annual runoff. These extreme estimates come from the high global warming scenario. For comparison the range from the low global warming scenario is a -14 to a -1 percent change in mean annual runoff. The main sources of uncertainty are in the global warming projections and the global climate modelling of local rainfall response to the global warming. The uncertainty in the rainfall-runoff modelling of climate change impact on runoff is small compared to the climate change projections.

The projected growth in commercial forestry plantations is negligible. The total farm dam storage volume over the region is projected to increase by 8.7 GL or 8 percent by ~2030. The best estimate of the combined impact of climate change and farm dam development is a 14 percent reduction in mean annual runoff. Extreme estimates range from a -44 to a -3 percent reduction. The modelled reduction in mean annual runoff from the projected increase in farm dams alone is about 0.5 percent which is very small compared to the runoff reduction in the median climate change projection.

3.5 References

BRS (2005) 1993, 1996, 1998 and 2000 Land Use of the Murray-Darling Basin, Version 2. Resource Identifier: ID01. Online digital dataset and spatial data layer. File identifier: http://adl.brs.gov.au/findit/metadata_files/a_mdblur9abl_00711a00.xml Product access: http://data.brs.gov.au/anrdl/a_mdblur9abl_00711a00.xml

Chiew FHS, Vaze J, Viney N, Jordan P, Perraud J-M, Zhang L, Teng J, Pena J, Morden R, Freebairn A, Austin J, Hill P, Wiesenfeld C and Murphy R (2008) Rainfall-runoff modelling across the Murray-Darling Basin. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia. In prep.

DSE (2004) Victoria in Future 2004 – Population projections. Department of Sustainability and Environment, Victoria. Available at: www.dse.vic.gov.au

IPCC (2007) Climate Change 2007: The Physical Basis. Contributions of Working Group 1 to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press.

Potter NJ, Chiew FHS, Frost AJ, Srikanthan R, McMahon TA, Peel MC and Austin JM (2008) Characterisation of recent rainfall and runoff across the Murray-Darling Basin. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia. In prep.

Victorian Government (1989) Water Act 1989, Act Number 80/1989. Parliament of Victoria.


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4 River system modelling This chapter includes information on the river system modelling for the Goulburn-Broken region. It has four sections:

• a summary • an explanation of the regional modelling approach • a presentation and description of results • a discussion of key findings.

The information in this chapter is derived from the calibrated Goulburn Simulation Model (GSM) REALM representation of the Goulburn, Broken, Loddon and Campaspe river systems provided by the Victorian Department of Sustainability and Environment (DSE).

4.1 Summary


The Goulburn-Broken region includes the Goulburn River and its tributaries, the largest being the Broken River which joins the Goulburn River near Shepparton. The Goulburn River flows into the Murray River upstream of Echuca. Major towns within the region include Shepparton, Alexandra and Seymour. The Goulburn-Broken region is connected to the Campaspe, Loddon-Avoca and Wimmera regions via the Waranga Western Channel.

River system modelling for the Goulburn-Broken region includes the following modelling scenarios:

• Scenario O This scenario represents a GSM system configuration similar to that used by DSE for planning purposes. Run from May 1891 to June 2006, it represents the current level of development. No groundwater behaviour derived from interaction with surrounding groundwater models was applied for this scenario, although the model does include unattributed gains and losses. Scenario O includes post-unbundling of entitlements into high and low reliability water products, as well as the restored Winton Swamp (formerly Lake Mokoan).

• Scenario A – historical climate and current development This scenario is based on the Scenario O model with current level of development but is run for the common historical climate period used in this project (July 1895 to June 2006). Additionally, Scenario A incorporates groundwater behaviour derived from interaction with surrounding groundwater models. This scenario is the baseline scenario against which scenarios B, C and D are compared.

• Scenario P – without-development This scenario incorporates the model for Scenario A and covers the common historical climate period. Current levels of development such as public storages and demand nodes are removed from the model to represent without-development conditions. Natural water bodies, fixed diversion structures and existing catchment runoff characteristics are not adjusted.

• Scenario B – recent climate and current development This scenario represents a future climate condition if the climate observed in the region since 1997 is to persist into the future. The level of development is the same as Scenario A. For Scenario B, a without-development model run is also undertaken; this uses Scenario B climate and Scenario P development conditions.

• Scenario C – future climate and current development Scenarios Cwet, Cmid and Cdry represent a range of future climate conditions that are derived by adjusting the historical climate and flow inputs used in Scenario A (Chapter 3). The level of development is the same as Scenario A. For each Scenario Cwet, Cmid and Cdry, without-development model runs are also undertaken; these use Scenario C climate and Scenario P development conditions.

• Scenarios D – future climate and future development Scenarios Dwet, Dmid and Ddry incorporate Scenario C, with flow inputs adjusted for 2030 estimates of development in farm dams and commercial forestry plantations. The impact of groundwater development on


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river reaches is also considered. The farm dam and forestry projections are discussed in Chapter 3, while groundwater development is discussed in Chapter 6.

These scenarios may not eventuate but they encompass consequences that might arise if no management changes were made. Consequently results from this assessment highlight pressure points in the system, both now and in the future. This assessment does not elaborate on what management actions might be taken to address any of these pressure points.

The Goulburn and Broken river system model represents the current utilisation of entitlements. Modelled crop areas are fixed and do not reflect any change in irrigated area as a function of available water resources. Crop demands are derived independently based on various factors including rainfall and evaporation.

The findings in this report are based on current water sharing and management strategies. Adaptive management processes required under Victorian legislation include long-term water resource assessments and sustainable water strategies that assist in ensuring the level of equity desired by the broader community is achieved. Thus, water sharing and management arrangement may adapt over time to future water resources conditions.

The Goulburn River is both a gaining and losing stream at different times of the year. The average annual flow under without-development conditions and for the historical climate (Scenario P) over the modelling period is 3233 GL/year at the end of the system, downstream of McCoy’s Bridge (at 405232).

4.1.2 Key messages

• The current average annual surface water availability for the region is 3233 GL/year. Current average surface water diversions (including water supplied and channel and pipe losses) within the Goulburn-Broken region are 1099 GL/year. A further 507 GL/year is transferred to the Campaspe, Loddon-Avoca and Wimmera regions via the Waranga Western Channel. The relative level of surface water use for the region is defined as the ratio of total surface water diversions (including water transferred to other regions) to water availability. The current relative level of surface water use is extremely high at 50 percent.

• Reliability of supply is determined separately for high reliability water shares (HRWS) and low reliability water shares (LRWS) and is reported for allocations in February. In the regulated Goulburn system, a 100 percent HRWS allocation occurs in 97 percent of years and the minimum HRWS allocation is 73 percent. A 100 percent LRWS allocation occurs in 42 percent of years and a zero LRWS allocation occurs in 24 percent of years. In the regulated Broken system, a 100 percent HRWS allocation occurs in 88 percent of years and the minimum HRWS allocation is 1 percent. A 100 percent LRWS allocation occurs in 84 percent of years and a zero LRWS allocation occurs in 11 percent of years.

• If the climate of the last ten years were to continue, average surface water availability would be reduced by 41 percent and end-of-system flows on the Goulburn River at McCoy’s Bridge would be reduced by 58 percent. The volume of water diverted for use within the region would be reduced by 25 percent. In the regulated Goulburn system, a 100 percent HRWS allocation would occur in 49 percent of years and the minimum HRWS allocation would be 8 percent. A 100 percent LRWS allocation would occur in 2 percent of years and a zero LRWS allocation would occur in 88 percent of years. In the regulated Broken system, a 100 percent HRWS allocation would occur in 52 percent of years and the minimum HRWS allocation would be 1 percent. A 100 percent LRWS allocation would occur in 48 percent of years and a zero LRWS allocation would occur in 47 percent of years. Transfers to other regions via the Waranga Western Channel would be reduced by 25 percent. The relative level of use for the region would rise to 63 percent.

• Under the best estimate (or median) 2030 climate, average surface water availability would be reduced by 14 percent and end-of-system flows at McCoy’s Bridge would be reduced by 22 percent. Water diversion for use within the region would decrease by 5 percent. In the regulated Goulburn system, a 100 percent HRWS allocation would occur in 87 percent of years and the minimum HRWS allocation would be 29 percent. A 100 percent LRWS allocation would occur in 21 percent of years and a zero LRWS allocation would occur in 36 percent of years. In the regulated Broken system, a 100 percent HRWS allocation would occur in 83 percent of years and the minimum HRWS allocation would be 1 percent. A 100 percent LRWS allocation would occur in 79 percent of years and a zero LRWS allocation would occur in 17 percent of years. Transfers to regions via the


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Waranga Western Channel would be reduced by 5 percent. The relative level of use for the region would rise to 54 percent.

• Under the wet 2030 climate extreme, average surface water availability would be reduced by 3 percent. Overall, there would be little impact on the volume of water diverted for use or on the reliability of supply. However, Goulburn River outflows would be reduced by 6 percent. Under the dry extreme 2030 climate, conditions would be slightly more severe than under a continuation of the climate of the last ten years. Water availability would be reduced by 45 percent, water use within the region would be reduced by 29 percent, end-of-system flows on the Goulburn would be reduced by 62 percent and the volumes of water transferred out of the region via the Waranga Western Channel would be reduced by 32 percent. Reliability of supply would be similar to a continuation of the recent climate for the Broken system but would be substantially worse for the Goulburn system. For example, in the Goulburn system a 100 percent HRWS allocation would occur in 33 percent of years and the minimum HRWS allocation would be 4 percent.

• Projected future development of small farm dams and increases in groundwater extraction would have minor impacts on streamflow and surface water use.

4.1.3 Robustness

A trial run of the model using inputs representing extremely dry climate conditions was made to assess how robustly it would behave. Allocations to irrigation districts and private diverters during this trial run went down to 4 percent for the Goulburn system and 1 percent for the Broken system. The combined headworks storage was drawn-down to 453.6 GL. The model behaved robustly. The model’s response to increases and decreases in inputs was reasonable. The change in diversions and end-of-systems flows was consistent with the change in inflows. Mass balance over the modelling period was maintained within 1 percent for all scenarios.

4.2 Modelling approach

The following section provides a summary of the generic river modelling approach, a description of the GSM model and how it was developed. Refer to Chapter 1 for more context on the overall project methodology.

4.2.1 General

River system models that encapsulate descriptions of current infrastructure, water demands, and water management and sharing rules were used to assess the implications of the changes in inflows on the reliability of water supply to users. River system models currently employed by state agencies and the Murray-Darling Basin Commission were used due to time constraints and the need to link the assessments to state water planning processes. The main models used are IQQM, REALM, MSM-BigMod, WaterCress and a model of the Snowy Mountains Hydro-electric Scheme.

4.2.2 Description of river model for the Goulburn-Broken region

The GSM spans three reporting regions: the Goulburn-Broken, Campaspe and Loddon-Avoca. These three regions are modelled as one because they are hydrologically linked by the Waranga Western Channel which transfers water from the Goulburn-Broken to the Campaspe and on to the Loddon-Avoca (Figure 4-1). The Waranga Western Channel continues on from the Loddon-Avoca through to the Wimmera region. However, this connection is not shown on Figure 4-1 because the GSM is not linked to the river model for the Wimmera. Rather, the Wimmera model is calibrated to observed inflows from the Waranga Western Channel.

The GSM is a REALM (V5.01) representation of the Goulburn, Broken, Campaspe and Loddon river systems. The Broken River flows into the Goulburn River near Shepparton, and the Goulburn, Campaspe and Loddon rivers are all linked via the Waranga Western Channel (DSE, 2005). Therefore, changes in one part of the GSM can affect flows and reliability of supply in other GSM river systems. The GSM was recently updated and covers the period of May 1891 to December 2006 (SKM, 2007). The common reporting period for this project is July 1895 to June 2006. The GSM is comprised of over 350 nodes and over 780 links, all arranged into the four river systems, the Waranga Western Channel


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and several water accounting functions. The Goulburn River is modelled from Lake Eildon to downstream of McCoy’s Bridge. The Broken River is modelled from Lake Nillahcootie to where it joins with the Goulburn River near Shepparton.

Figure 4-1. The full extent of the Goulburn Simulation Model across the Goulburn-Broken, Campaspe and Loddon-Avoca regions, indicating how the Waranga Western Chanel links across the three regions

A schematic of the Goulburn-Broken river system model is shown in Figure 4-2. Components outside of the region are not included. The Goulburn and Broken river system models are part of the GSM which was run simultaneously for the Campaspe, Goulburn-Broken and Loddon-Avoca regions.

The Goulburn-Broken region consists of the Goulburn and Broken systems, the Waranga Basin, the Waranga Western Channel and the irrigation districts this channel supplies through to downstream of Greens Lake. The model includes significant losses from the Goulburn River at several locations. The largest is from the reach between Eildon and Goulburn Weir. Losses also occur from the East Goulburn Main Channel, the Waranga Western Channel and the channels supplying the irrigation districts. The largest storage is Lake Eildon. Other storages modelled with varying degrees of regulation include Goulburn Weir, Lake Nillahcootie, Winton Swamp, Waranga Basin and Greens Lake (Table 4-1).

The majority of water for consumptive use is diverted to the Waranga Western Channel (average of 1233 GL/year). Diversions to the East Goulburn Main Channel and private diverters take from the river an average of 345 GL/year and 49 GL/year respectively. Most of the total urban water demand is from towns in the lower Goulburn region. Water use is


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modelled by three stock and domestic demand nodes, 11 private diverter demand nodes, six irrigation demand nodes and two urban demand nodes (Table 4-2). Water supply to the environment is delivered in the model by specifying instream demands at particular locations in the river to be supplied from the environment’s entitlement (Table 4-3).

Figure 4-2. River system map showing subcatchments, inflow and demand nodes and gauge locations within the Goulburn-Broken region


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Table 4-1. Storages in the river model in the Goulburn-Broken region

Reservoirs Active storage Average annual Inflow

Average annual regulated release

Average annual net evaporation

Degree of regulation

GL GL/y Lake Eildon 3290.0 1475.6 1392.7 2.8 0.9 Goulburn Weir 25.5 2698.5 2689.8 8.6 1.0 Waranga Basin 411.0 1053.7 1011.8 38.3 1.0 Greens Lake 27.9 19.4 13.2 6.1 1.0 Lake Nillahcootie 39.5 62.0 15.1 4.9 0.3 Winton Swamp 25.7 21.7 0.0 13.5 0.6 Region total 3819.7 5330.9 5122.7 74.2 4.9

Table 4-2. Water use configuration in the model

Number of nodes Entitlement Pump constraints

Model notes

GL/y ML/d Urban 2 various Stock and domestic part of 7 nodes 35.4 various High Reliability Water Share part of 13 nodes 746.1 various Low Reliability Water Share Irrigation part of 15 nodes 283.2 various Includes significant delivery losses Environment part of 9 nodes 66.6 various Subtotal part of 15 nodes 349.8 various

Table 4-3. Water management in the model

Accounting system Notes Goulburn-Murray Water Authority Based on a ten year rolling average for the section between Lake Eildon and

Goulburn Weir Environmental flow requirements Period Minimum flows Goulburn River d/s Eildon 120 ML/d Goulburn River d/s Eildon 2950 ML/month if cumulative 24 month inflows are

greater than the trigger Goulburn River d/s Goulburn Weir 250 ML/d Goulburn River at McCoy’s Bridge Nov to June 350 ML/d July to Oct 400 ML/d Broken River d/s Lake Nillahcootie June to Nov 30 ML/d or natural if Lake Nillahcootie is not spilling Broken River u/s Casey Weir Dec to May 22 ML/d or natural flow Broken River d/s Casey Weir Dec to May 25 ML/d or natural flow Holland Creek d/s Holland Weir 12 ML/d or natural flow Supply rates Max extraction rate Goulburn River at Goulburn Weir to East Goulburn main channel

80 GL/month capacity

Goulburn Weir to Cattanach and Stuart Murray canals

213 GL/month capacity

4.2.3 Model setup

The original GSM and associated REALM V5.01 executable code were obtained from DSE. This model was run for the original period of May 1891 to June 2006 and validated against previous results. The model conditions assume post-unbundling of entitlements and a reduction in the capacity of the Winton Swamp (formerly Lake Mokoan) from 362 GL to 77 GL. A without-development version of this model was created by removing all headworks storages and service basins, consumptive demands and channel systems.


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The Goulburn and Broken rivers contain a significant amount of total storage relative to inflows. The initial state of these storages can influence the results obtained. Each scenario has a one month warm-up period (June 1895) for the storages hence the storage conditions for 31 May 1895 need to be determined. To do this, Scenario O (which begins on 1 May 1891) was started with all of the storages empty at 30 April 1891 and run up to 31 May 1895 and the final storage volumes were recorded. This was repeated with all of the storages initially full. The modelling results (Figure 4-5) show that the storage traces nearly converge for the two runs by 31 May 1895 (the exception being Lake Eildon). An average of the storage volumes starting from empty and full was adopted where storage volumes are different at this point.

The model was configured for an extremely dry climate trial run (broadly equivalent to Scenario Cdry). The rainfall, evaporation and inflows were varied (Table 4-4) to represent spatial variability of changes to climate and flow. The model test run appeared to be robust overall with low allocations being reached (Figure 4-5) and no significant changes in model convergence.

Table 4-4. Rainfall, evaporation and flow factors for model robustness trial run

Season Rainfall Evaporation Flow DJF 0.86 1.07 0.43–0.67MAM 0.95–0.96 1.08 0.67–0.92JJA 0.86 1.05 0.43–0.65SON 0.71 1.07–1.08 0.33–0.57


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Table 4-5. Model setup information

Original models Version Start date End date Goulburn Simulation Model (GSM) REALM 5.0 May-1891 June-2006Connection Goulburn River Outflow downstream of McCoy’s Bridge Waranga Western Channel Outflow to Campaspe region Baseline models Warm-up period REALM 5.01 June-1895 June-1895Modelling period REALM 5.01 July-1895 June-2006Goulburn River Outflow downstream of McCoy’s Bridge Waranga Western Channel Outflow to Campaspe region Modifications Data No adjustment required Inflows No adjustment required Groundwater loss nodes Nodes added to system Initial storage volumes Scenario O was run to May 1895 with initial storages full and empty. Average

of storages at May 1895 taken. Warm-up test results Setting initial storage volumes Storages

commence emptyStorages

commence full Difference Percent of full

volume GL percent Lake Eildon storage volume 31/05/1895 2331.1 2388.6 57.5 1.7Goulburn Weir storage volume 31/05/1895 17.9 17.9 0.0 0.0Waranga Basin storage volume 31/05/1895 169.9 169.9 0.0 0.0Greens Lake storage volume 31/05/1895 15.2 15.2 0.0 0.0Lake Nillahcootie storage volume 31/05/1895 19.8 19.8 0.0 0.0Winton Swamp storage volume 31/05/1895 12.9 12.9 0.0 0.0Rain rejection storage volume 31/05/1895 0 0 0.0 0.0Original models Storage vol. end of May (1895–2006) Mean Median Full storage capacity GL Lake Eildon 1756.3 1775.0 3290Goulburn Weir 18.8 17.9 25.51Waranga Basin 204.5 177.6 411Greens Lake 17.0 15.2 32.44Lake Nillahcootie 23.4 23.0 40.21Winton Swamp 6.8 5.0 27Rain rejection 0.5 0.2 1.1Robustness test results Original model Robustness test Minimum allocation in February

Goulburn private diverters and irrigators 73% 4% Goulburn urban users 86% 49% Broken private diverters (%) 1% 1%

Minimum combined system storage volume (GL) 630.4 453.6


4.3.1 River system water balance

The modelled mass balance for the Goulburn-Broken region is given in Table 4-6. Scenario O and Scenario A fluxes are displayed as GL/year and all other scenarios are presented as a percentage change from Scenario A. The averaging period for Scenario O differs from Scenario A.


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The directly gauged inflows represent inflows based on river gauges. The indirectly gauged inflows represent the inflows that are derived to achieve mass balance between mainstream gauges. The water supply was split into four categories: licensed private diverters, irrigation districts, stock and domestic, and urban. End-of-system flows are shown for the two main outflow points (downstream of McCoy’s Bridge and west of the Greens Lake offtake on the Waranga Western Channel). The change in storage between 30 June 1895 and 30 June 2006 averaged over the 111-year period is also included.

Appendix B contains mass balance tables for designated subcatchments in the model. The mass balance of each of the river reaches and the overall mass balance was checked by taking the difference between total inflows and outflows of the system. The mass balance error was less than 1 percent in all cases.

The water balance (Table 4-6) shows catchment inflows decrease under all future climate scenarios and that there would be a reduction in inflows of 13 percent under Scenario Cmid. Water supplied in the Goulburn-Broken region decreases by around 6 percent under Scenario Cmid. Losses decrease under future climate scenarios as there is less water in the system to be lost. End-of-system flows for the Goulburn River decrease under all future scenarios and there would be a 22 percent reduction under Scenario Cmid. Scenario D results are similar to Scenario C.


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Table 4-6. River system model average annual water balance in the Goulburn-Broken region under scenarios O, A, B, C and D

O A B Cwet Cmid Cdry Dwet Dmid DdryModel start date May-1891 Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895Model end date Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006

GL/y percent change from Scenario A Storage volume Change over period -13.2 -13.5 34% 14% 31% 33% 14% 31% 33%Inflows Subcatchments

Directly gauged 375.8 365.6 -52% -2% -15% -48% -3% -16% -48%Indirectly gauged 3043.2 3030.4 -39% -3% -13% -44% -3% -14% -44%Irrigation drainage returns 28.6 28.4 -43% -4% -15% -46% -4% -15% -47%Sub-total 3447.6 3424.4 -40% -3% -13% -44% -3% -14% -45%

River groundwater gains* 0.0 0.3 -13% 7% -1% -17% 1% -9% -33%Sub-total 3447.6 3424.7 -40% -3% -13% -44% -3% -14% -45%Diversions Water use

Licensed private diverters 49.4 49.4 -16% 4% 0% -13% 4% 0% -14%Irrigation districts 718.2 715.2 -30% -1% -7% -36% -2% -7% -37%Stock and domestic 6.9 6.8 0% 0% 0% 0% 0% 0% 0%Urban supply 19.1 19.1 0% 0% 0% 0% 0% 0% 0%Sub-total 793.6 790.5 -28% -1% -6% -34% -1% -7% -34%

Channel / pipe loss 310.3 308.4 -14% -1% -4% -17% -1% -4% -17%Sub-total 1103.9 1098.9 -25% -1% -6% -29% -1% -6% -30%Outflows System outflow

D/S McCoy's Bridge 1602.6 1585.2 -58% -5% -22% -62% -6% -23% -62%To Campaspe via Waranga Western Channel

507.9 506.9 -25% 0% -5% -32% 0% -5% -32%

River groundwater loss** 0.0 0.4 -53% -8% -20% -55% -4% -15% -50%Sub-total 2110.5 2092.5 -50% -4% -18% -55% -5% -19% -55%

Net evaporation*** 73.2 74.2 -11% 13% 9% 18% 12% 8% 18%Sub-total 2183.6 2166.7 -49% -3% -17% -52% -4% -18% -53%Unattributed fluxes

River unattributed loss 173.3 172.6 -33% -2% -10% -38% -2% -10% -38%* Values in the row are those used in the river modelling. The correct value for Scenario A, to be consistent with the groundwater modelling, is 9.2 GL/year. The percentage change values for other scenarios are correct. See the next paragraph for more information. ** Values in the row are those used in the river modelling. The correct value for Scenario A, to be consistent with the groundwater modelling, is 11.8 GL/year. The percentage change values for other scenarios are correct. See the next paragraph for more information. *** Evaporation from private licensed storages (GL/year) is not included as it is already accounted in diversions.

During the report reviewing process, it was discovered that a unit conversion error had been made in translating the groundwater modelling results for input to the river modelling. Rerunning the river modelling was not practical at review stage as the river model (GSM) spans three regions, and is linked to the river models for the Murray and Murrumbidgee regions. The impact on the river modelling results is minor and is footnoted in Table 4-6. The values affected are small compared to other water balance terms, and have only minor impact on other river modelling results presented in this chapter. The main caveat is that the absolute values of end-of-system flows (Section 4.3.5) at low flows should be interpreted with some caution, and the relative level of use values (Table 4-12) would be up to 1 percent lower than reported if the groundwater-river fluxes were fully and properly accounted for in the river modelling.

4.3.2 Waranga Western Channel

The outflow from this region into the Waranga Western Channel has been included in the average annual balance table (Table 4-6). The modelled mass balance for the entire Waranga Western Channel is given in (Table 4-7). Scenario A fluxes are displayed as GL/year and all other scenarios are presented as a percentage change from Scenario A.


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The inflows from each of the regions into the Waranga Western Channel are presented. The water supply was split by region into three categories: irrigation districts, stock and domestic, and urban. End-of-system flows are shown for Waranga Western Channel to the Wimmera region. The regional outflows are not included in the mass balance but are provided for each region at the end of the table. The change in storage between 30 June 1895 and 30 June 2006 averaged over the 111-year period is also included.

Table 4-7. Average annual water balance for the Waranga Western Channel under scenarios A, B, C and D

A B Cwet Cmid Cdry Dwet Dmid DdryModel start date Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895Model end date Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 GL/y percent change from Scenario A Storage volume Change over period 0.3 -328% -78% -344% -328% -81% -344% -332%Inflows Regions

Goulburn-Broken Indirectly gauged 4.6 -48% -2% -15% -48% -2% -15% -48%Transfers from Goulburn Weir 1232.8 -24% -1% -5% -28% -1% -5% -28%

Sub-total 1237.3 -24% -1% -5% -28% -1% -6% -29%Campaspe

From Campaspe River to Waranga Western Channel

11.5 -85% -6% -25% -84% -6% -28% -84%

Loddon-Avoca Loddon Weir inflows 66.4 -45% -4% -15% -51% -6% -15% -51%

Sub-total 1315.2 -26% -1% -6% -30% -1% -6% -30%Diversions Water use

Goulburn-Broken Irrigation districts 469.5 -31% -2% -8% -38% -2% -8% -38%

Campaspe Irrigation districts 224.7 -30% -1% -7% -36% -1% -7% -37%Urban diversions 1.0 0% 0% 0% 0% 0% 0% 0%Sub-total 225.7 -30% -1% -7% -36% -1% -7% -36%

Loddon-Avoca Irrigation districts 256.5 -29% -1% -6% -35% -1% -6% -35%Stock and domestic 1.9 0% -1% -1% 0% -1% -1% 0%Sub-total 258.4 -29% -1% -6% -35% -1% -6% -35%

Channel / pipe loss 307.2 -14% -1% -4% -16% -1% -4% -16%Sub-total 1260.9 -26% -1% -6% -32% -1% -7% -32%Outflows System outflow

To Wimmera 6.3 0% 0% 0% 0% 0% 0% 0%Net evaporation* 44.4 -12% 8% 5% 14% 8% 5% 14%Sub-total 50.6 -10% 7% 4% 12% 7% 4% 12%Unattributed fluxes River unattributed loss 3.4 -3% 0% -1% -2% 0% -1% -2%Regional outflows (not included in mass balance)

Goulburn-Broken to Campaspe 506.9 -25% 0% -5% -32% 0% -5% -32%Campaspe to Loddon-Avoca 263.6 -24% 0% -4% -30% 0% -4% -30%Loddon-Avoca to Wimmera 6.3 0% 0% 0% 0% 0% 0% 0%

* Evaporation from private licensed storages (GL/year) is not included as it is already accounted in diversions


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4.3.3 Inflows and water availability

Inflows

There are several ways to provide an indication of water availability. The most obvious way is to use the total inflow, which is the sum of all of the inflows in the model. For the Goulburn-Broken region, this is 3425 GL/year prior to instream losses being taken into account under Scenario A. An alternative is to locate the point of maximum average annual flow in the river system under without-development conditions. As all river models are calibrated to achieve mass balance at mainstream gauges, the gauge with maximum average annual flow is a common reference across all models irrespective of how mass balance is calibrated. The without-development conditions remove the influences of upstream extractions and regulation and give a reasonable indication of total inflows without the influence of development.

A comparison between scenarios under without-development conditions for reaches along the Goulburn River is presented in Figure 4-3. It shows that the maximum average annual mainstream flow occurs at the end of the modelled system downstream of McCoy’s Bridge (405232) with a value of 3233 GL/year under Scenario A. The difference between this value and total system inflow is the instream losses and change in natural lake storage volume under without-development conditions.

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Water availability

Water availability is a function of climate, and thus is assessed for without-development conditions for scenarios A, B and C. For the Goulburn-Broken region, the without-development annual mainstream flow downstream McCoy’s Bridge (gauge 405232) is used to define water availability (Figure 4-3). Table 4-8 shows the average water availability under scenarios A, B and C in GL/year and the relative change in water availability under scenarios B and C. There are substantial reductions in water availability under scenarios B, Cmid and Cdry. The leakage induced by current groundwater use implicit in model calibration is assumed to be negligible (<0.05 GL/year), and no adjustment is therefore required to the modelled average streamflow in assessment of water availability.

Table 4-8. Average annual surface water availability downstream McCoy’s Bridge under scenarios A, B and C (assessed for without-development conditions, which for Scenario A is synonymous with Scenario P)

A B Cwet Cmid Cdry GL/y Total surface water availability (modelled without-development maximum average mainstream flow)

3233.1 1911.2 3146.3 2792.3 1787.8

percent change from Scenario A Change in surface water availability -41% -3% -14% -45%


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A time series of annual water availability under Scenario A is shown in Figure 4-4. Water availability varies between 9320 GL in 1955 down to 730 GL in 1914. Figure 4-5 shows the changes in annual water availability from Scenario A under scenarios B and C. The largest changes in water availability occur under without-development scenarios B and C. The large ’spikes’ on Figure 4-5 typically occur in high water availability years under Scenario A.

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Figure 4-5. Difference in annual water availability for the region under scenarios B and C relative to Scenario A

4.3.4 Storage behaviour

The modelled behaviour of major public storages in the Goulburn-Broken region gives an indication of the level of regulation of a system and how reliable the storages are during extended periods of low or no inflows. Table 4-9 shows the lowest recorded combined storage volume and the corresponding date for each of the scenarios. The average and maximum years between spills is also provided. A spill event commences when the sum of the total system storages exceeds 95 percent of the combined full supply volume and ends when the sum of the total system storages falls below 85 percent of full supply volume. A spill occurs at 95 percent of full supply level because some individual storages will spill at times when total system storage is not at full supply level. The end condition is used to include in a spill event period when the dam is close to full and oscillates between spilling and just below full. The time between spills increases slightly under scenarios Cwet and Dwet and spills rarely occur under the scenarios Cdry and Ddry.


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Table 4-9. Details of storage behaviour in the Goulburn-Broken region

Total headworks storages A B Cwet Cmid Cdry Dwet Dmid DdryMinimum storage volume (ML) 531,213 449,346 518,243 514,917 432,620 523,389 514,590 430,721Minimum storage date 04/1915 06/1998 04/1915 04/1915 06/1998 04/1915 04/1983 06/1912Average years between spills 3.3 36.7 4.4 7.5 110.6* 4.5 7.5 110.6*Maximum years between spills 15.8 49.5 16.6 17.6 110.6* 16.6 17.6 110.6**Only one spill occurs over the modelling period for these scenarios

The time series of total headworks storage behaviour during the severe drought over the last ten years of the project modelling period show that under the dry scenarios (B, Cdry and Ddry) the total system storage is lower at the start of the drought and is drawn-down to much lower levels than under Scenario A (Figure 4-6). Scenario Cmid has the combined storage consistently lower than Scenario A.

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Figure 4-6. Total Goulburn-Broken headworks storage behaviour over the period of lowest storage content under (a) scenarios A and B, (b) scenarios Cwet, Cmid and Cdry and (c) scenarios Dwet, Dmid and Ddry

4.3.5 Consumptive water use

Water use

Table 4-10 shows the average annual water use for different river reaches under Scenario A and the percentage changes under all other scenarios compared to Scenario A. Figure 4-7 shows average annual water use under all scenarios for reaches of the Goulburn River from upstream to downstream. This reach-by-reach presentation of water use provides a very coarse indication of the changes from upstream to downstream.


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Table 4-10. Change in total water use in each subcatchment relative to Scenario A

Reach A B Cwet Cmid Cdry Dwet Dmid Ddry GL/y percent change from Scenario A Tributaries into Lake Eildon 0.0 0% 0% 0% 0% 0% 0% 0%Goulburn River d/s of Lake Eildon to d/s Goulburn Weir (including East Goulburn Main Channel)

263.3 -26% 0% -6% -31% 0% -6% -32%

Waranga Western Channel from Waranga basin to d/s Greens Lake offtake

469.5 -31% -2% -8% -38% -2% -8% -38%

Goulburn River from d/s Goulburn Weir to d/s Shepparton 17.5 -4% 1% 0% -5% 1% 0% -5%Goulburn River from d/s Shepparton to d/s McCoy's Bridge 19.8 -20% 3% -2% -25% 3% -2% -25%Broken River to u/s Casey's Weir 1.9 -10% 6% 3% 3% 6% 3% 3%Broken River from Casey's Weir to Goulburn River confluence

18.5 -12% 2% 1% -7% 2% 0% -7%

Total 790.5 -28% -1% -6% -34% -1% -7% -34%

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Figure 4-7. Average annual water use from upstream to downstream Goulburn River under (a) scenarios A, B and C and (b) scenarios A, B and D

Figure 4-8(a) shows the annual time series of total water supplied under Scenario A and Figure 4-8(b)-(d) show the difference in annual volumes under the other scenarios relative to Scenario A. The maximum and minimum annual total water use under Scenario A is 911 GL in 1981 and 496 GL in 2002, respectively.


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Table 4-11 shows the annual total water use for the lowest one-, three- and five-year periods as well as the average annual total water use under Scenario A and the percentage change from Scenario A under each other scenario. These figures indicate the impact of the scenarios on water use during dry periods and on average.

Table 4-11. Annual total surface water use under scenarios A, B, C and D

A B Cwet Cmid Cdry Dwet Dmid Ddry GL/y percent change from Scenario A Lowest 1-year period 496.6 -84% -22% -54% -89% -24% -56% -88%Lowest 3-year period 601.8 -52% -6% -19% -60% -6% -19% -60%Lowest 5-year period 622.5 -48% -3% -17% -56% -4% -18% -56%Average 790.5 -28% -1% -6% -34% -1% -7% -34%

Level of use

The level of use is defined here as the ratio of the total use to water availability. Total use consists of total net diversions from the Goulburn and Broken rivers and their tributaries, as well as groundwater usage and future farm dam impacts. Total net diversions include the 507 GL of water diverted from the Goulburn River to the Campaspe region via the Waranga Western Channel, plus channel delivery losses within the Goulburn-Broken region. Water availability is defined as in Section 4.3.2. Table 4-12 shows the level of use under each of the scenarios. The level of use does not change markedly between scenarios.

Table 4-12. Level of water use under scenarios A, B, C and D

A B Cwet Cmid Cdry Dwet Dmid Ddry GL/y Total surface water availability 3233.1 1911.2 3146.3 2792.3 1787.8 3146.3 2792.3 1787.8

GL/y

Subcatchment use Groundwater use impacts 0 0 0 0 0 4.2 4.1 4.2Future farm dam impacts - - - - - 9.1 9 8.9

Streamflow use Water diversion for use within region 1098.9 824.2 1087.9 1033.0 780.2 1087.9 1033.0 769.2Water transfer to other regions 506.9 380.2 506.9 481.6 344.7 506.9 481.6 344.7Leakage induced by groundwater use* 0.1 -0.1 0 0 -0.1 0.1 0.1 0

Total use 1605.9 1204.3 1594.8 1514.5 1124.8 1608.2 1527.7 1127.0

percent Relative level of use 50% 63% 51% 54% 63% 51% 55% 63%* See footnotes * and ** to Table 4-6

Reliability of supply

An indication of the reliability of supply is given by the percentage of years in which available water is less than the maximum allocation. Reliability of supply is reported for allocations in February, which is representative of the final allocations. Reliability of supply for individual water products is shown in Figure 4-9. The Y-axis is the percentage of the maximum allocation in February. The dry scenario variants significantly reduce the percentage of time in which available water is below the maximum allocation.

The Goulburn private diverters and irrigators receive the maximum LRWS allocation in 21 percent of years under Scenario Cmid compared to 42 percent under Scenario A. The Broken private diverters receive their maximum LRWS


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February allocation 79 percent of the time under Scenario Cmid compared to 84 percent under Scenario A. The urban demands are not significantly affected.

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Figure 4-9. Reliability of (a) High Reliability Water Share and (b) Low Reliability Water Share supply in the Goulburn-Broken River system for Goulburn Irrigation Areas and Private Diverters; (c) Goulburn Urbans; and (d) High Reliability Water Share and (e) Low

Reliability Water Share Broken Private Diverters under scenarios A, B, C and D


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Figure 4-8 (cont’). Reliability of (a) High Reliability Water Share and (b) Low Reliability Water Share supply in the Goulburn-Broken River system for Goulburn Irrigation Areas and Private Diverters; (c) Goulburn Urbans; and (d) High Reliability Water Share and (e) Low

Reliability Water Share Broken Private Diverters under scenarios A, B, C and D

The reliability of total demand in the Goulburn-Broken region under each scenario is illustrated in Figure 4-10. The Y-axis represents the percentage of unrestricted demand that is supplied. Unrestricted demand is the amount of water desired by a consumer but this full amount may not be supplied due to water restrictions. All future climate scenarios (scenarios C and D) result in a decrease in the reliability of the supply.


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Figure 4-10. Total volume of water use as a percentage of demand for the Goulburn-Broken region under (a) scenarios A, B and C and (b) scenarios A, B and D

4.3.6 River flow behaviour

The river flow behaviour in the Goulburn-Broken region is examined at three locations throughout the system: the Goulburn River upstream of Goulburn Weir (mid-system flow), the Broken River at the confluence with the Goulburn River (mid-system flow), and the Goulburn River downstream of McCoy’s Bridge (end-of-system flow).

Mid-system flow characteristics

Figure 4-11 shows the flow duration curves for the Broken River upstream of the Goulburn confluence and the Goulburn River upstream of Goulburn Weir (mid-system flows). The cease-to-flow percentiles under these scenarios are presented in Table 4-13. Cease-to-flow is considered to occur when model flows are less than 1 ML/month. Neither the Broken nor the Goulburn rivers cease-to-flow under any of the scenarios. Scenario P in these graphs represents without-development conditions with current climate.


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Figure 4-11. Monthly flow duration curves at Broken River upstream of the Goulburn confluence under (a) scenarios P, A, B and C and (b) scenarios P, A, B and D, and at Goulburn River upstream of Goulburn Weir under (c) scenarios P, A, B and C and

(d) scenarios P, A, B and D

Table 4-14 shows the size of monthly events with two-, five- and ten-year recurrence intervals under scenarios P, A, B, C and D. This analysis estimates the peak monthly flow (as the model uses a monthly time step) and not the peak flow for a day, which would be considerably higher. The table shows that there are large reductions in the size of peak monthly flows for the dry climate scenario variants and are greater than 50 percent in most cases.

Table 4-13. Cease-to-flow at mid-system locations in percentage time under scenarios P, A, B, C and D

Outflow Name P A B Cwet Cmid Cdry Dwet Dmid DdryBroken River u/s Goulburn confluence 0% 0% 0% 0% 0% 0% 0% 0% 0%Goulburn River u/s Goulburn Weir 0% 0% 0% 0% 0% 0% 0% 0% 0%


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Table 4-14. Monthly flow event frequency for mid system locations Broken River at the confluence with Goulburn River and Goulburn River upstream of Goulburn Weir under scenarios P, A, B, C and D

Return interval P A B Cwet Cmid Cdry Dwet Dmid Ddryyears ML/month percent change from Scenario A

Broken River upstream of Goulburn confluence 2 63,335 55,119 -59% -5% -23% -58% -5% -24% -58%5 129,337 117,539 -60% -1% -20% -57% -1% -20% -58%

10 151,199 146,341 -54% 2% -15% -49% 2% -15% -50%Goulburn River upstream of Goulburn Weir

2 603,181 329,837 -6% 0% 0% -18% 0% 0% -18%5 945,520 512,949 -36% -1% -17% -36% -2% -19% -36%

10 1,118,530 740,832 -55% -7% -26% -55% -8% -31% -55%

Figure 4-12 shows the mean monthly flow under scenarios P, A, B, C and D for the two mid-system flow locations. The flow pattern upstream of Goulburn Weir has changed quite significantly compared to Scenario P due to the winter storage and summer release of water for irrigation between Lake Eildon and Goulburn Weir.

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Figure 4-12. Seasonal plots at Broken River upstream of the Goulburn confluence under (a) scenarios P, A, B and C, and (b) scenarios P, A, B and D and at Goulburn River upstream of Goulburn Weir under (c) scenarios P, A, B and C, and

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End-of-system flow characteristics

Figure 4-13 shows the flow duration curves for the Goulburn River downstream of McCoy’s Bridge (end-of-system flow). The cease-to-flow percentiles under these scenarios are presented in Table 4-15. Cease-to-flow is considered to occur when model flows are less than 1 ML/month. The Goulburn River always flows even under the dry scenarios.

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Figure 4-13. Monthly flow duration curves at Goulburn River downstream of McCoy’s Bridge (end-of-system) under (a) scenarios P, A, B and C, and (b) scenarios P, A, B and D

Table 4-16 shows the size of monthly events with two-, five- and ten-year recurrence intervals under scenarios P, A, B, C and D. This analysis estimates the average peak monthly flow (as the model uses a monthly time step) and not the peak flow for a day, which is considerably higher. The table shows that there are large reductions in the size of events for the dry climate scenarios at greater than 50 percent.

Table 4-15. Cease-to-flow at Goulburn River downstream of McCoy’s Bridge (end-of-system) in percentage time under scenarios P, A, B, C and D

Outflow Name P A B Cwet Cmid Cdry Dwet Dmid DdryGoulburn River d/s McCoy's Bridge (EOS) 0% 0% 0% 0% 0% 0% 0% 0% 0%

Table 4-16. Monthly flow event frequency at Goulburn River downstream of McCoy’s Bridge (end-of-system) under scenarios P, A, B, C and D

Return interval P A B Cwet Cmid Cdry Dwet Dmid Ddryyears ML/month percent change from Scenario A

2 722,451 341,976 -71% -8% -30% -74% -9% -31% -74%5 1,215,104 760,405 -57% -3% -22% -63% -4% -23% -64%

10 1,429,693 954,229 -55% -9% -26% -56% -9% -27% -57%

Figure 4-14 shows the mean monthly flow under scenarios P, A, B, C and D for the end-of-system flow location. The post-development (scenarios B, C and D) flow patterns have the seasonality restored compared to the mid-river flow pattern (Figure 4-12). This is most likely due to the unseasonal flows being diverted to various water users and the addition of new catchment inflows downstream of Goulburn Weir.


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Figure 4-14. Seasonal plots at Goulburn River downstream of McCoy’s Bridge (end-of-system) under (a) scenarios P, A, B and C, and (b) scenarios P, A, B and D

4.3.7 Share of available resource

Non-diverted water

There are several ways of considering the relative impact of scenarios on non-diverted water and Table 4-17 presents two indicators: the ratio of average annual non-diverted water to average water availability; and the ratio of average annual non-diverted water to Scenario A average annual non-diverted water.

Table 4-17. Relative level of available water not diverted for use under scenarios A, B, C and D

Relative level of non-diverted water A B Cwet Cmid Cdry Dwet Dmid DdryNon-diverted water as a percentage of total available water 50% 37% 49% 46% 37% 49% 45% 37%Non-diverted share relative to Scenario A non-diverted share 100% 43% 95% 78% 41% 95% 78% 40%

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4.3.8 Inter-region water supply reliability

Water users in the Goulburn system are located in the Goulburn-Broken, Campaspe and Loddon-Avoca regions and are connected by the Waranga Western Channel. Separate allocations are also announced for users in areas supplied predominantly or exclusively by the Campaspe and Loddon rivers.

Table 4-18 show the water supply reliability under scenarios A, B and C for each of the Goulburn, Broken, Campaspe and Loddon systems. Results under Scenario D are similar to Scenario C and thus are not presented. Water allocations in the different systems are determined based on the storage size, inflows, demands and other factors in each supply system. Reliability of the Goulburn system is comparable with the Loddon system and slightly lower than the Campaspe system. Further discussion of the reliability of supply in the Campaspe and Loddon-Avoca system is in CSIRO (2008a, 2008b).

Table 4-18. Inter-region comparison of water supply reliability under scenarios A, B and C

Percentage of years which receive

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Minimum HRWS February allocation

Percentage of years which receive zero LRWS allocation

Scenario A Goulburn system 97% 42% 73% 24%Broken system 88% 84% 1% 11%Campaspe system 99% 74% 76% 10%Loddon system 92% 42% 58% 24%Scenario B Goulburn system 49% 2% 8% 88%Broken system 52% 48% 1% 47%Campaspe system 77% 24% 8% 46%Loddon system 47% 2% 1% 88%Scenario Cwet Goulburn system 95% 36% 54% 27%Broken system 86% 81% 1% 14%Campaspe system 98% 71% 43% 17%Loddon system 91% 36% 47% 27%Scenario Cmid Goulburn system 87% 21% 29% 36%Broken system 83% 79% 1% 17%Campaspe system 97% 67% 33% 17%Loddon system 83% 21% 15% 36%Scenario Cdry Goulburn system 33% 1% 4% 93%Broken system 54% 49% 1% 45%Campaspe system 83% 37% 13% 33%Loddon system 32% 1% 1% 93%


4.4.1 Model configuration

The GSM, which includes the Goulburn-Broken region, was recently updated and covers the period of May 1891 to December 2006 (SKM, 2007). The common reporting period for this project is July 1895 to June 2006. Table 4-6 shows that the average annual inflow over the previous modelling period is 3448 GL/year while for the common modelling period it is 3424 GL/year. This difference is due to averaging the inflows over different time periods. The model conditions assume post-unbundling of entitlements and restored Winton Swamp (formerly Lake Mokoan).


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4.4.2 Comparative use

The Goulburn River has a reasonably high degree of regulation (Table 4-1). The Broken River is less regulated. Irrigation is the largest water user in the Goulburn-Broken and supplied via the Waranga Western Channel and East Goulburn Main Channel.

Water diversion is 1099 GL/year on average. A further 507 GL/year is transferred to the Campaspe, Loddon-Avoca and Wimmera regions via the Waranga Western Channel. Reliability of supply is reported for allocations in February. Water users in the regulated Goulburn system receive the maximum February allocation from their HRWS in 97 percent of years and a minimum February allocation of 73 percent. They receive the maximum February allocation from their LRWS in 42 percent of years and a minimum February allocation (zero) of LRWS in 24 percent of years. Water users in the Broken system receive the maximum February allocation from their HRWS in 88 percent of years and a minimum February allocation of 1 percent. They receive the maximum February allocation from their LRWS in 84 percent of years and a minimum February allocation (zero) of LRWS in 11 percent of years.

4.4.3 Scenarios

Scenario Cwet is slightly drier than historical climate condition and would show a reduction in inflows of around 3 percent. Water use would be reduced by 1 percent and there would be a reduction in Goulburn outflows downstream of McCoy’s Bridge of 5 percent.

Scenario Cmid would show a reduction in inflows of 13 percent. Supply to consumptive users drops by around 6 percent, but urban water users are largely unaffected. Water users in the regulated Goulburn system would receive the maximum February allocation from their HRWS in 87 percent of years and a minimum February allocation of 29 percent. They would receive the maximum February allocation from their LRWS in 21 percent of years and a minimum February allocation (zero) in 36 percent of years. Water users in the Broken system would be subject to lower, but still significant reductions in reliability of supply. End-of-system outflow for the Goulburn (downstream of McCoy’s Bridge) would be reduced by around 22 percent. Losses decrease because less water is available in the supply system.

Scenarios B, Cdry and Ddry result in a reduction in inflows of around 40 to 45 percent. Supply to consumptive users drops by around 28 to 34 percent, but again urban water users are not as affected. The maximum HRWS February allocation for the Goulburn system would only be available in 31 to 49 percent of years whilst a LRWS allocation would only be available in 6 to 12 percent of years. Water users in the Broken system would be subject to lower, but still significant reductions in reliability of supply. End-of-system outflow for the Goulburn River would be reduced by around 58 to 62 percent. The proportion of time with no outflow from the system does not change, but there is a large reduction in average outflow volumes. Losses decrease because less water is available in the supply system. The total headworks storage volume for the last 10 years of drought starts lower than it did historically, and the combined storage is drawn down to very low levels.

Scenario D results do not differ significantly from the current level of development. The projected effects of future small catchment dam and groundwater development are minor compared to the impacts of climate change.

4.5 References

CSIRO (2008a) Water availability in the Campaspe. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia.

CSIRO (2008b) Water availability in the Loddon-Avoca. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia.

DSE (2005) Goulburn Simulation Model – Calibration for the Murray Darling Basin Cap. Department of Sustainability and Environment, Victoria, Melbourne. Water allocation, Water Sector Group.

SKM (2007) Goulburn Simulation Model Update of Inputs 2007. Final. 27 August 2007. Prepared for Goulburn-Murray Water and the Department of Sustainability and Environment by Sinclair Knight Merz.


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5 Uncertainty in surface water modelling results This chapter describes the assessment of uncertainty in the surface water modelling results. It has four sections:

• a summary • an overview of the approach • a presentation and description of results • a discussion of key findings.

5.1 Summary

The uncertainty that is internal to the river model (as opposed to that associated with the scenarios), and the implications that this has for confidence in the results and their appropriate use, are assessed using multiple lines of evidence. This involves comparing: (i) the river model to historical gauged main stem flows and diversions, which are its main points of reference to actual conditions, and (ii) ungauged inferred inflows and losses in the model to independent data on inflows and losses to ascertain if they can be attributed to known processes. These two aspects of model performance were then combined with some other measures to assess how well the model might predict future patterns of flow.


• The Goulburn-Broken surface water system is well gauged. The region has a climate and streamflow gauging network that is denser than the Murray-Darling Basin (MDB) average. Its rainfall gauging network is around three times denser and its streamflow gauging network more than five times denser than the average MDB density. The distribution of rainfall and streamflow gauges is even. The understanding of the Goulburn-Broken surface water hydrology is generally good.

• Water accounts were developed for seven reaches for the period 1990 to 2006. Five reaches covered the Goulburn River between Lake Eildon and McCoy Bridge and two reaches covered the Broken River between Lake Nillahcootie and Goorambat. The accounts include a large part of the runoff generated in the region but not all of the diversions in the region.

• Overall model performance appears to be very good to excellent for the accounted reaches. Main stem inflows, outflows and diversions differs by less than 10 percent between the river model and accounts. Total ungauged inflows are within 21 percent. The greatest uncertainty is in unattributed losses in the lower Goulburn River which are more than 150 GL/year (5 percent of estimated inflows).

5.1.2 Key messages

• The river model for the Goulburn-Broken region reproduces observed streamflow patterns very well and produces estimated water balance terms that are similar to water accounts in all the assessed reaches.

• The model provides moderate to very strong evidence that changes in flow pattern would occur under the dry and best estimate 2030 climates. Evidence that changes in flow pattern would occur under the wet 2030 climate is weak to modest.

• The model provides reasonable to strong evidence of changes in flow pattern related to water resource development to-date for the Goulburn River but not for the Broken River. The changes due to projected future development are less than 2 percent of changes predicted under climate change for the reaches assessed.

• Overall the model is well suited for the purposes of this project. Predictions of changes in low flows patterns are assigned a low level of confidence.


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5.2 Approach

5.2.1 General

A river model is used in Chapter 4 to analyse expected changes in water balance, flow patterns and consequent water security under climate and/or development change scenarios. Uncertainty in the analysis can be external or internal:

• External uncertainty is external to the model. It includes uncertainty associated with the forcing data used in the model, determined by processes outside the model such as climate processes, land use and water resources development.

• Internal uncertainty relates to predictive uncertainty in the river model that is an imperfect representation of reality. It can include uncertainty associated with the conceptual model, the algorithms and software code it is expressed in, and its specific application to a region (Refsgaard and Henriksen, 2004).

Full measurement of uncertainty is impossible. The analysis focuses on internal uncertainty. When scenarios take the model beyond circumstances that have been observed in the past, measurable uncertainty may only be a small part of total uncertainty (Weiss, 2003; Bredehoeft, 2005). The approach to addressing internal uncertainty involved combining quantitative analysis with qualitative interpretation of the model adequacy (similar to ‘model pedigree’, cf. Funtowicz and Ravetz, 1990; Van der Sluijs et al., 2005) using multiple lines of evidence. The lines of evidence are:

• the quality of the hydrological observation network • the components of total estimated stream flow gains and losses that are directly gauged, or can easily be

attributed using additional observations and knowledge, respectively, through water accounting • characteristics of model conceptualisation, assumptions and calibration • the confidence with which the water balance can be estimated, through comparison of water balances from the

baseline river model simulations and from water accounting • measures of the baseline model’s performance in simulating observed stream flow patterns • the projected changes in flow pattern under the scenarios compared to the performance of the model in

reproducing historical flow patterns.

None of these lines of evidence are conclusive in their own right. In particular:

• the model may be ‘right for the wrong reasons’. For example, by having compensating errors • there is no absolute ‘reference’ truth, all observations inherently have errors and the water accounts developed

here use models and inference to attribute water balance components that were not directly measured, and • adequate reproduction of historically observed patterns does not guarantee that reliable predictions about the

future are produced. This is particularly so if model boundary conditions are outside historically observed conditions, such as in climate change studies.

Qualitative model assessment is preferably done by consulting experts (Refsgaard et al., 2006). The timing of the project prevented this. Instead a tentative assessment of model performance is reviewed by research area experts within and outside the project as well as stakeholder representatives.

The likelihood that the river model gives realistic estimates of the changes that would occur under the scenarios evaluated is assessed within the above limitations.

Overall river model uncertainty is the sum of internal and external uncertainty. The range of results under different scenarios in this project provides an indication of the external uncertainty. River model improvements will reduce overall uncertainty only where internal uncertainty clearly exceeds the external uncertainty.

The implication of overall uncertainty on the use of the results presented in this project depends on: (i) the magnitude of the assessed change and the level of threat that this implies, and (ii) the acceptable level of risk (Pappenberger and Beven, 2006). This is largely a subjective assessment and is not attempted herein. A possible framework for considering the implications of the assessed uncertainties is shown in Table 5-1.


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Table 5-1. Framework for considering implications of assessed uncertainties

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Current water sharing arrangements are likely to be inadequate for ongoing management of water resources, as they do not adequately consider future threats.

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Current water sharing arrangements may be inadequate for ongoing management of water resources. Further work to reduce the major sources of uncertainty can help guide changes to water sharing arrangements.

5.2.2 Information sources

Information on the gauging network was obtained from the Water Resources Station Catalogue (www.bom.gov.au/hydro/wrsc) and the Victorian Water Resources Data Warehouse (www.vicwaterdata.net ). Information on the REALM river model was provided in SKM (2006), DSE (2005) and MDBC (2006). Time series of water balance components as modelled under the baseline scenario (Scenario A) and all other scenarios were derived as described in Chapter 4. The data used in water accounting are described in the following section.

5.2.3 Water balance accounting

Purpose

Generic aspects of the water accounting methods are described in Chapter 1. This section includes a description of the basic purpose of the accounts: to inform the uncertainty analysis using an independent set of the different water balance components by reach and by month. The descriptions in Chapter 1 also cover the aspects of the remote sensing analyses used to estimate wetland and irrigation water use and inform calculations for attribution of apparent ungauged gains and losses. Aspects of the methods that are region specific are presented below.

Framework

Water accounts for 1990 to 2006 were developed for seven reaches. Five reaches covered the Goulburn River between Lake Eildon and McCoy Bridge and two reaches covered Broken River between Lake Nillahcootie and Goorambat. The associated subcatchments are shown in Figure 5-1 and are related to water accounting reaches in Table 5-2. The accounts include a large part of the runoff generated but not all of the diversions. Figure 5-1 shows associated catchment areas, accounting reaches and contributing catchments. Ephemeral waterbodies and floodplain areas are subject to periodic inundation. Black dots and red lines are nodes and links in the river model respectively.


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Table 5-2. Comparison of water accounting reaches with reach codes used in runoff modelling

Water accounting reach Subcatchment code(s) Description 1 4042061 Broken River @ Moorngag 2 4042161, 4042122, 4042163, 4042190 Broken River @ Goorambat 3 4052013, 4052014, 4052015 Goulburn River @ Trawool 4 4052594 Goulburn River @ Seymour 5 4052593 Goulburn River @ Murchison 6 4052042, 4052692, 4042243 Goulburn River @ Shepparton 7 4052321 Goulburn River @ McCoy Bridge Not assessed Reason 4042181 Upstream inflow to Reach 1 4052580 Upstream inflow to Reach 3 4052595 Direct inflow to Reach 5 4042082 Direct inflow to Reach 2

4042041, 4042141, 4042041 4042103, 4067041 D/S of the last available gauging station, runoff may flow to the Murray River

4052043 Flow does not contribute to any reaches

Figure 5-1. Map showing the subcatchments used in modelling, and the water accounting reaches


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5.2.4 Diversion data

Wetland and irrigation water use

The results of the remote sensing analyses (Chapter 1) are in Figure 5-1. It shows extensive irrigation areas below Murchison Weir, four lakes (Eildon, Nillahcootie, Waranga Basin and Winton Swamp) and several ephemeral wetlands on the Goulburn River floodplain. Streamflow and diversion data were provided by Sinclair Knight Merz (SKM, 2006).

Calculation and attribution of apparent ungauged gains and losses

Calculation and attribution of apparent ungauged gains and losses were undertaken according to the methods described in Chapter 1.

5.2.5 Model uncertainty analysis

The river model results and water accounts were used to derive measures of model uncertainty. The different analyses are described below. Details on the equations used to calculate the indicators can be found in Van Dijk et al. (2008). Calculations were made for each reach separately but summary indicators were compared between reaches.

Completeness of hydrological observation network

Statistics on how well all the estimated river gains and losses were gauged – or where not gauged, how well these could be attributed based on additional observations and modelling – were calculated for each reach:

• the volumes of water measured at gauging stations and off-takes, as a fraction of the grand totals of all estimated inflows or gains, and/or all outflows or losses, respectively

• the fraction of month-to-month variation in the above terms • the same calculations as above, but for the sum of gauged terms plus water balance terms that could be

attributed using the water accounting methods.

The results of this analysis for annual totals are also presented in Appendix C.

Comparison of modelled and accounted reach water balance

The water balance terms for river reaches were compared for the water accounting period as modelled under Scenario A and as accounted. Large divergence is likely to indicate large uncertainty in reach water fluxes and therefore uncertainty in the river model and water accounts.

Climate range

If the model calibration period is characterised by climate conditions that are a small subset, or atypical of the range of climate conditions that was historically observed, this increases the chance that the model will behave in unexpected ways for climate conditions outside the calibration range. The percentage of the overall climate variability range for the 111-year climate sequence that was covered by the extremes in the calibration period was calculated as an indicator.

Performance of the river model in explaining historical flow patterns

All the indicators used in this analysis are based on the Nash-Sutcliffe model efficiency (NSME; Nash and Sutcliffe, 1970). NSME indicates the fraction of observed variability in flow patterns that is accurately reproduced by the model. In addition to NSME values for monthly and annual outflows, values were calculated for log-transformed and ranked flows, and high (highest 10 percent) and low (lowest 10 percent) monthly flows. NSME cannot be calculated for the log-transformed flows where observed monthly flows include zero values or for low flows if more than 10 percent of months have zero flow. NSME is used to calculate the efficiency of the water accounts in explaining observed outflows.

This indicates the scope for model improvements to explain more of the observed variability. If NSME is much higher for the water accounts than for the model, it suggests that the model can be improved to reduce uncertainty. If similar,


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additional hydrological data may be required to support a better model. A visual comparison of streamflow patterns at the end-of-reach gauge with the flows predicted by the baseline river model and the outflows that could be accounted was done for monthly and annual time series and for monthly flow duration curves

Scenario change-uncertainty ratio

Streamflow patterns simulated for any of the future scenarios can be compared to those for the baseline scenario. If these future scenarios explain historically observed flows about as well or better than the baseline scenario, then it may be concluded that the future scenario changes are within model ‘noise’, that is, smaller or similar to model uncertainty.

Conversely, if the agreement between scenario flows and historically observed flows is poor – much poorer than between the baseline model and observations – then the model uncertainty is smaller than the modelled change, and the modelled change can be meaningfully interpreted.

The metric used to test this hypothesis is the change-uncertainty ratio. The definition was modified from Bormann (2005) and calculated as the ratio of the NSME value for the scenario model to that for the baseline (Scenario A) model. A value of around 1.0 or less suggests that the projected scenario change is not significant when compared to river model uncertainty.

A ratio that is considerably greater than 1.0 indicates that the future scenario model is much poorer at producing historical observations than the baseline model, suggesting that the scenario leads to significant changes in flow. The change-uncertainty ratio is calculated for monthly and annual values, in case the baseline model reproduces annual patterns well but not monthly patterns. The same information was plotted as annual time series, monthly flow duration curves and a graphical comparison made of monthly and annual change-uncertainty ratios for each scenario.

5.3 Results

5.3.1 Density of the gauging network

Figure 5-2 shows the location of streamflow, rainfall, and evaporation gauges in the region and Table 5-3 provides information on the measurement network. The Goulburn-Broken region is the third most densely gauged region in the MDB. The density of the streamflow, rainfall and evaporation gauging networks is respectively about three, five and four times the average MDB density. There is an even distribution of streamflow and rainfall gauges. Evaporation gauges are concentrated in the irrigation areas and near Lake Eildon and Winton Swamp.

Table 5-3. Some characteristics of the gauging network of the Goulburn-Broken region (22,378 km2) compared with the entire Murray-Darling Basin (1,062,443 km2)

Gauging network characteristics Goulburn-Broken Murray-Darling Basin Number per 1000 km2 Number per 1000 km2 Rainfall Total stations 369 16.49 6232 5.87Stations active since 1990 226 10.10 3222 3.03Average years of record 45 45 Streamflow Total stations 122 5.45 1090 1.03Stations active since 1990 100 4.47 881 0.83Average years of record 16 20 Evaporation Total stations 13 0.58 152 0.14Stations active since 1990 8 0.36 104 0.10Average years of record 24 27


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Figure 5-2. Map showing the rainfall, stream flow and evaporation observation network, along with the subcatchments used in modelling

5.3.2 Review of model calibration and evaluation information

Model description

The original REALM Goulburn Simulation Model (GSM) was developed in the 1980s. It expanded gradually and then was refined with a major update in 1995. The GSM simulates the harvesting and supply of water from the major water supply systems and is used extensively by water authorities and the Victorian Government for operational purposes and to develop water policy in those valleys. The model was the starting point for the re-calibration (to 1993/94 level of development) associated with the MDBC’s cap on surface water diversion audit process. The latest GSM update extends input files to June 2006 (SKM, 2006).

The GSM covers the valleys of the Goulburn, Loddon and Campaspe Rivers and Broken River. They form a connected water management system because of the Waranga Western Channel that is used to transfer water between the valleys. The whole system has 20 storages. The whole GSM contains 58 ‘demand areas’ (a localised group of water users). Storages are generally used for resource allocation in their immediate valley, but can also supplement resources in adjacent valleys: the Loddon, Campaspe and Broken systems can supplement the Goulburn system, while the Goulburn and Broken systems can supplement the Murray system with specific allocation and supply rules that are included in the model. Water movement within and between the four valleys is simulated by a monthly REALM model.


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The model is used for the implementation of bulk entitlements, although its monthly time step limits its ability to closely simulate some river operations and short-term variability (MDBC, 2006). Irrigation demands are estimated using the PRIDE (PRogram for Irrigation DEmands) model. PRIDE models crop water requirements without considering management constraints, which are considered in the REALM model itself. PRIDE simulates rural demands for ten GSM bulk supply irrigation areas: Shepparton, Rodney, Tongala, Deakin, Rochester East, Rochester West, Tandara, Dingee, Campaspe, and Boort. Private diverters along supply routes also extract significant volumes of water from waterways. Private diversions are modelled in the Broken, Goulburn, and Campaspe catchments. Diversions simulated by the model represent approximately 98.5 percent of the total diversions from the Goulburn-Broken and Loddon designated valleys.

Data availability and use

The GSM requires monthly inflows to storages and tributary flows at selected locations, monthly demands, and rainfall and evaporation. There are 21 inflow, five rainfall, five evaporation and 58 demand values for the entire model required for each month of simulation. Input data were initially provided for the period June 1896 to July 1989, but have since been extended annually, and currently extend until June 2006. Specifics about the streamflow gauging station and climate data were available for the 2006 update (SKM, 2006) but may be different from the same data used for initial model development and calibration. Table 5-4 lists the streamflow gauging stations and the period of the record used in the Goulburn-Broken part of the model. Gaps in streamflow records were filled through regression analysis of data from nearby stations and interpolation. The PRIDE model required daily evaporation and rainfall data, crop factors and crop areas to simulate irrigation demand. Urban demands were generally estimated from regression equations that use evaporation, rainfall and temperature data.


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Table 5-4. Streamflow gauging stations for which data were used in the Goulburn-Broken REALM model

Station Description Calibration period Use Broken River 404204 Boosey Creek @ Tungamah 1917 to date Broken catchment inflows 404206 Broken River @ Moorngag 1957 to date Back Creek inflow 404207 Holland Creek @ Kelfeera 1960 to date Broken catchment inflows 404208 Moonee Creek @ Lima 1963 to date Broken catchment inflows 404218 Lake Nillahcootie Head Gauge 1967 to date Back Creek inflow 404220 Lake Nillahcootie Outlet 1968 Back Creek inflow Goulburn River 405200 Goulburn River @ Murchison 1881 to date Inflows between Trawool and Goulburn Weir 405201

Goulburn River @ Trawool 1925 to date Inflows between Eildon and Trawool, and between Trawool and Goulburn Weir

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Goulburn River @ Eildon 1916 to date Eildon water balance; Inflows between Eildon and Trawool; and between Trawool and Goulburn Weir

405205 Murrindindi River above “Cowells” 1939 to date Inflows between Eildon and Trawool 405209 Acheron River at Taggerty 1955 to date Inflows between Eildon and Trawool 405212 Sunday Creek @ Tullarook 1947 to date Inflows between Trawool and Goulburn Weir 405214 Delatite River @ Tonga Bridge 1945 to date Lake Eildon water balance 405215 Howqua River @ Glen Esk 1947 to date Lake Eildon water balance 405217 Yea River @ Devlins Bridge 1954 to date Inflows between Eildon and Trawool 405218 Jamieson River @ Gerrans Bridge 1954 to date Lake Eildon water balance 405219 Goulburn River @ Dohertys 1954 to date Lake Eildon water balance 405226 Pranjip Creek @ Moorilim 1957 to date P.C.S. Creek inflow 405227 Big River @ Jamieson 1958 to date Lake Eildon water balance 405228 Hughes Creek @ Tarcombe Rd 1958 to date Inflows between Trawool and Goulburn Weir 405229 Wanalta Creek @ Wanalta 1960 to date Waranga inflow 405231 King Parrot Creek @ Flowerdale 1961 to date Inflows between Eildon and Trawool 405237 Seven Creek @ Euroa 1945 to date Infilling of 405269 405240 Sugarloaf Creek @ Ash Bridge 1966 to date Inflows between Trawool and Goulburn Weir 405241 Rubicon River @ Rubicon 1922 to date Inflows between Eildon and Trawool 405245 Ford Creek @ Mansfield 1970 to date Lake Eildon water balance 405246 Castle Creek @ Arcadia 1970 to date P.C.S Creek inflow 405248 Major Creek @ Graytown 1971 to date Inflows between Trawool and Goulburn Weir 405251 Brankeet Creek @ Ancona 1971 to date Lake Eildon water balance 405269 Seven Creek @ Kailla West 1977 to date P.C.S. Creek inflow 405274 Home Creek @ Yarck 1977 to date Inflows between Eildon and Trawool 405700 Stuart Murray Channel @ Offtake 1892 to date Inflows between Trawool and Goulburn Weir 405702 Cattanach Canal @ Waranga Inlet 2004 to date Inflows between Trawool and Goulburn Weir 405704 East Goulburn Main Channel @ 8km

flume 2004 to date Inflows between Trawool and Goulburn Weir

Model calibration

Demand was a critical aspect of model calibration for the Cap model (MDBC, 2006). Initial estimates of irrigation demands were obtained from the PRIDE demand models developed for bulk entitlement conversions. These were re-run with daily rainfall and evaporation data from 1992 to 1995 (with estimated 1993/94 crop areas). Monthly demand was simulated ‘at the farm gate’. The actual amount supplied may be less due to shortage or channel capacity constraints. GSM was first run with unrestricted demands and then restriction and rationing rules were applied to estimate what could be supplied to each demand zone. Simulated total volumes supplied for the calibration period (1992 to 1995) were compared with recorded volumes. Estimated crop areas were adjusted where there was a difference in the PRIDE model and the process repeated until a good match was obtained.


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Model verification was done for the two-year period from mid-1995 to mid-1997. An allowance was made in interpreting model performance for measurement and modelling errors and the effect of the cap measures that reduced demands below 1993/94 levels.

Simulated cumulative diversions for the combined five years of simulations (calibration and verification periods combined) were compared with recorded diversions at selected sites. Demand calibration was done for offtakes and therefore additional checks were made to ensure that the modelled river diversions (including delivery losses) also matched historical diversions. Comparisons were made on Waranga Basin losses as well as an overall monthly water balance check for each valley (inflow, outflow, demand and storage). Modelled and recorded storage behaviour and end-of-system flows for each river valley were compared for 1992 to 2004.

The water balance check included the portion of the system supplied directly from the Goulburn River and that supplied from the Waranga Western Channel. The check on Waranga Basin losses revealed that modelled diversions from Goulburn Weir to Waranga Basin were about 5 to 6 percent less than recorded over the calibration period. These losses related to the outflow from the Waranga Basin to the various irrigation channels and errors in measurement of flows in channels going into or out of the Waranga Basin. Analysis of measurement accuracy revealed sporadic errors in the recorded data that reduced the unaccounted losses in some years when corrected (DSE, 2005). Monthly estimates of losses were obtained from a water balance calculation using the revised recorded inflows and outflows (post 1980) and allowing for evaporation from water surfaces. The seepage from the Waranga Basin was believed to be minimal. Unaccounted losses in Waranga Basin were ignored prior to 1980. Modelled and recorded storage behaviour were compared for the period of 1992 to 2004 as an indicator of model calibration performance. Reproduction of end-of-valley flows was also tested. The Broken River flows into the lower Goulburn River before it reaches the Murray River, so the Broken River outflow is part of the Goulburn River outlfow.

Model performance assessment

The model over estimated total diversions for the Goulburn system by less than 0.1 percent per year over the calibration period. The model over estimated total diversions by 0.6 percent per year when the two-year verification period was included. These volumes are very small relative to the annual volumes diverted and were within expected model error. The cumulative difference in diversions was typically around 10 percent for individual demand nodes. The overestimation from 1995 to 1997 coincided with capping measures such as the 100 percent limit on sales allocations and restraints on trading. MDBC surface water cap measures reduced diversions below 1993/94 operating rule impacts.

The model under estimated diversions for the Broken system by 2.5 percent per year over the calibration period. The under estimate was only by 1.1 percent per year when the two-year verification period was included. Estimation of diversions in the combined valleys was very good. The model over estimated diversions by only 0.4 percent per year and the seasonal variation was reproduced closely over the calibration and verification periods.

Total historical storage behaviour in Lake Eildon and Waranga Basin reproduced well. The model over estimated the total volume in store in 1994 and 1995. The modelled outflow from the Goulburn valley to the Murray matched the historical flow closely. Inflows to Trawool storage were under estimated in the 2006 model update. Inflows to Goulburn Weir were over estimated and a re-examination of the methods was recommended (SKM, 2006). The storage behaviour in Lake Nillahcootie (Broken system) departed from the historical behaviour because of the difficulty in modelling their operation.

The annual rise and fall is represented reasonably well by the model (MDBC, 2006).

Model results for a period of 21 years starting in 1983, historical storage levels and diversions growth were used to calculate key statistics for model errors. A standard error of 4.2 percent was reported for the Goulburn-Broken and Loddon indicating that the model accurately represents their diversions.

Model improvements and uncertainties

There are some uncertainties in the way the model operated and some system components and processes were insufficiently represented in the model.


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Change required included:

• Further Identification of the physical basis of Waranga Basin losses and the measured flows in and out of the Basin. The model’s loss calculation methodology may be improved as losses are investigated.

• The Murray-Darling Basin Commission identified that transmission losses were modelled as fixed percentages of flows and variation of these losses with flow was not considered in the Broken River supplement to the Murray (MDBC, 2006). This assumption leads to uncertainty particularly under a different climate regime where losses may become greater or smaller than assumed by the model.

5.3.3 Model uncertainty analysis

The river model results and water accounts were used to derive measures of model uncertainty. The different analyses are described below. In the interest of brevity, details on the equations used to calculate the indicators are not provided here but can be found in Van Dijk et al. (2008). Calculations were made for each reach separately but summary indicators were compared between reaches.

Completeness of hydrological observation network

The estimated fraction of all gains and losses that is gauged is shown for each reach in Figure 5-3. Reaches 1 and 2 are in the Broken River and reaches 3 to 7 are in the Goulburn River. Conclusions follow:

• Gains are reasonably to extremely well gauged in the Goulburn River (62 to 97 percent) but poorly or moderately well gauged in the Broken River (25 to 51 percent).

• Outflows and losses are well to extremely well gauged (71 to 98 percent) in all reaches. The best is in the Goulburn River.

• Overall, 80 to 97 percent of the total water balance is gauged in the five Goulburn River reaches, but only 48 to 72 percent in the two Broken River reaches.

• Attribution of gains and losses using SIMHYD estimates of local runoff, diversion data and remote sensing helps to explain much of the remaining apparent ungauged gains and losses. This allows 89 to 97 percent of the combined reach gains and losses to be accounted in the Goulburn River. Most of the ungauged gains and losses in the Broken River can also be attributed (72 to 81 percent gauged or attributed).

• Most gains and losses are gauged or can be attributed so the water balance of the Goulburn River (and to a less extent the Broken River) is well understood.

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Comparison of modelled and accounted reach water balance

A summary of reach-by-reach water balances simulated by the river model and derived by water accounting can be found in Appendix C. Due to the REALM model structure the water balances for each of the upper three Goulburn River reaches (reaches 3, 4 and 5) could not be compared but their combined water balance could be compared. The total water balances for the seven accounted reaches are compared in Table 5-5.

Table 5-5. Regional water balance modelled and estimated on the basis of water accounting

Water balance (Jul 1990 – Jun 2006) Model (A) Accounts Difference Difference GL/y percent Inflows Main stem inflows 1445 1432 na na Tributary inflows 0 332 na na Local inflows 1512 941 571 61% Subtotal gains 2957 2704 253 9% Unattributed gains and noise - 547 na na Outflows End of system outflows 1262 1163 99 9% Distributary outflows 0 0 na na Net diversions 1518 1576 -58 -4% River flux to groundwater 0 0 na na River and floodplain losses 26 43 -17 -40% Unspecified losses 153 – na na Subtotal losses 2959 2781 177 6% Unattributed losses and noise - 483 na na na – not applicable.

An interpretation follows:

• Six of the seven reaches are gaining or have a very small net gain or loss. Only Reach 5 (Goulburn River between Seymour and Murchison) is strongly losing due to the diversion into Waranga Basin at Murchison Weir.

• The definition between tributary and local inflows varies between the model and the water accounting so only the sum of inflows were compared.

• There was no attempt to estimate groundwater exchanges in water accounting due to the lack of direct data. • Simulated main stem inflows into the Goulburn River above Lake Eildon and into the Broken River above Lake

Nillahcootie (1391 and 55 GL/year respectively) are 14 GL/year or 1 percent higher than accounted inflows (1401 and 30 GL/year respectively).

• Simulated main stem outflows from the Goulburn River below McCoy Bridge (1262 GL/year) is 99 GL/year or 9 percent higher than accounted (1163 GL/year).

• The sum of simulated local and tributary inflows (1512 GL/year) is 261 GL/year or 21 percent higher than the sum of accounted equivalent terms (gauged tributary inflows and SIMHYD estimates; 1251 GL/year). Similar relative differences occurred in all reaches. Some or all of the difference will be included in the 547 GL/year of apparent gains that could not be attributed in the accounts.

• Simulated diversions for the water accounting period (1518 GL/year) are 58 GL/year or 4 percent lower than those recorded (1576 GL/year).

• Simulated combined river and floodplain losses and unspecified losses (179 GL/year) are 131 GL/year or about four times higher than accounted river and floodplain losses (43 GL/year). This difference occurrs in the Goulburn River between Eildon Dam and Murchison (reaches 3, 4 and 5). The difference is in the 483 GL/year of unattributed losses and measurement error. Around 184 GL/year of this is associated with these same three reaches (Appendix C).

• Gauged water balance terms including diversions represent 69 percent of the total water balance. Another 15 percent can be attributed using SIMHYD local runoff estimates (941 GL/year) and estimates of river and floodplain losses (43 GL/year).


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• Unattributed gains are greater than unattributed losses for the entire accounted system. Combined unattributed gains (including measurement noise) represent 547 GL/year or 17 percent of total apparent gains, whereas unattributed losses (including measurement noise) represent 483 GL/year or 16 percent of total apparent losses. Their sum represents 16 percent of the total water balance.

• Overall the system is reasonably well gauged and understood. Main stem inflows, outflows and diversions were within 10 percent between the model and accounts. Total ungauged inflows were within 21 percent. The greatest uncertainty is associated with large unattributed losses that appear to occur in reaches 5 and 6.

Climate range

The calibration period used for the model was from 1992 to 1997. Ten years in the entire 111-year record used in modelling were drier than those included in this calibration period; eight years were wetter. The average rainfall for the calibration period (804 mm/year) was 5 percent higher than the long-term average (764 mm/year). The historical 111-year rainfall record had five years that were drier and eight years that were wetter than the extremes during the period of water accounting (1990 to 2006). Overall, although the period of calibration was short, it provided a reasonable representation of the longer climate record due to a dry 1994 (536 mm) and a wet 1992 (1003 mm). The water accounting period also provided a good representation of long-term climate variability and in particular included some drier more recent years.

Performance of the river model in explaining historical flow patterns

The better the baseline model simulates streamflow patterns, the greater the likelihood is that it represents the response of river flows to changed climate, land use and regulation changes (notwithstanding the possibility that the model is right for the wrong reasons through compensating errors). Appendix C lists indicators reach by reach of the model’s performance in reproducing different aspects of the patterns in historically measured monthly and annual flows (all are variants of Nash-Sutcliffe model efficiency).

Figure 5-4 shows the relative performance of the model in explaining observed streamflow pattern (as model efficiency) at the downstream gauge of accounted reaches, where model simulated results were available. Comparison of accounts with model results could not be made for reaches 3 and 4 in the Goulburn River system.

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Figure 5-4. Changes in the model efficiency (the performance of the river model in explaining observed streamflow patterns) along the length of the river (numbers refer to reach)


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Observations follow:

• Model performance for annual flow totals is very good to excellent (NSME=0.97–0.98) in all reaches except Reach 2 in the Broken River (NSME<0). Similarly, for monthly totals model performance is very good in the Goulburn River reaches (NSME=0.92–0.96) and in Reach 1 of the Broken River, but very poor in Reach 2 (NSME<0).

• With the exception of Reach 2, model performance in reproducing the 10 percent highest flows is very good to excellent in the Goulburn River (NSME=0.95–0.98) and good in Reach 1 in the Broken River (NSME=0.73).

• Performance in reproducing the 10 percent lowest flows is poor in all cases. This was mainly because low flows are strongly dominated by regulation and simulated river operations produced flow patterns that were different from real flow patterns. The model indicates streamflow in the Goulburn River is maintained between 30 and 40 GL/month during summer. Actual flows appear to be more variable and often lower (Appendix C).

• The simulated and observed flow duration curves agree reasonably well for all reaches except for the differences arising from the simulation of river regulation.

• End-of-system flow patterns in the Goulburn River below McCoy Bridge (Reach 7) are simulated very well (Figure 5-5).

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Scenario change-uncertainty ratio

A high change-uncertainty ratio (CUR) corresponds with a change in flows related to a scenario that is likely to be significant given the uncertainty, or noise, in the model. A CUR of around 1.0 indicates that the modelled change has a similar magnitude as the uncertainty in the model. The CUR for changes in monthly and annual total flow is shown in Figure 5-6. Model results were not available for reaches 3 and 4.


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Figure 5-6. Pattern along the river (numbers refer to reach) of the ratio of the projected change over the river model uncertainty for (a) monthly and (b) annual flows under scenarios P, C and D

Observations follow:

• CURs are generally smaller for monthly totals than for annual totals due to the greater variability in monthly flows that is harder to simulate than annual patterns.

• The significance of the simulated change under Scenario P to the current flow pattern is reasonably to very strong in the Goulburn River when compared to model performance (CUR of 13 to 119). Flows have reduced considerably across the flow range due to development (Appendix C). The significance of the simulated change under Scenario P to the current flow pattern was weak in the Broken River when compared to model performance (CUR of 1 to 2.5).

• The projected changes under Scenario Cdry are similar to those under Scenario B and almost identical to those under Scenario Ddry. The projected change is very strong compared to model uncertainty for annual totals (CUR of 29 to 48) and moderately to very strong for monthly flows (CUR of 3 to 17). The only exception was Reach 2 in the Broken River, where CUR values were lower because the model reproduced historical flows modestly (CUR of 0.8 to 1.3).

• The projected changes under scenarios Cmid and Dmid are of moderate to fair significance when compared to model uncertainty (CUR of 3 to 8) for monthly and annual flows. Scenarios Cwet and Dwet are only slightly significant (CUR of 0.9 to 2.4). Again these numbers were lower for Reach 2 (Figure 5-6).

• Scenario C and D impacts have almost identical CURs. Differences are 1 to 2 percent of the Goulburn River and zero to 1 percent of the Broken River average flows The scenarios produce no recognisable difference in annual total flows or the flow duration curve (Appendix C).

Conclusions follow:

• The model provides reasonable to strong evidence for changes in flow pattern due to development in the Goulburn River but weak evidence for the Broken River.

• The model provides moderate to very strong evidence that changes in flow pattern would occur under the dry and median climate change scenarios. Evidence that changes in flow would occur under the wet climate scenarios is weak to modest.

• The impact of projected development is very small when compared to the impact from projected climate change. • The model uncertainty for Reach 2 is large when compared to projected changes due to the poor simulation of

historical flow patterns in this reach particularly in the winter of 1994.


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5.4.1 Gauging and understanding of the hydrology of the Goulburn-Broken region

The Goulburn-Broken surface water system is well gauged. The density of gauging is greater than the MDB average. Streamflow and rainfall gauging stations are evenly distributed across the region. Water accounts were established for two reaches in Broken River and five in the Goulburn River. A comparison with model results could only be made for three of the five reaches. The Goulburn River reach that includes Murchison Weir is strongly losing due to diversion into Waranga Basin. All other reaches are gaining or had very small net changes in main river flow. Overall, the region appears to be sufficiently well gauged for reliable modelling. An estimated 69 percent of the total water balance is gauged, while an additional 15 percent can be attributed using additional independent observations and modelling.

The understanding of the hydrology of the Goulburn-Broken system is generally good. Groundwater interactions appear to play a minor role in the accounting section of the Goulburn-Broken surface water system and were not simulated by the river model. Surface water diversions are about 48 to 51 percent of total flow for the combined accounting reaches.

5.4.2 Model performance in explaining observations and comparison to water accounts

Overall model performance appears to be very good to excellent for the accounted reaches. Simulations are better in the Goulburn River than in the Broken River. Flows are not simulated well in the lower Broken River (Reach 2), particularly during the winter of 1994. This may be due to the observed flows including the behaviour of Lake Mokoan, whereas the model is simulating the behaviour of the restored Winton Swamp. Although the calibrated climate range is short it provided a reasonably good mix of wet and dry years that increases confidence in the reliability of the model under climate change scenarios.

The uncertainty analysis confirms that transmission losses are one of the more important sources of uncertainty in simulations and it is unclear how they will change in future (Section 5.3.2). The model simulates 153 GL/year of unspecified losses and 483 GL/year of apparent losses could not be attributed in water accounting. It represents 5 and 15 percent of estimated annual total inflows, respectively, given an indication of the likely impact on model uncertainty. River, floodplain and wetland losses are only estimated at 26 GL/year by the model and 43 GL/year in accounting and the nature of these losses is unclear. The greatest unattributed apparent losses occur in reaches 5 and 6 (the Goulburn River between Seymour and Shepparton).

Total simulated main stem, tributary and local inflows (2957 GL/year) are 294 GL/year less than apparent total gains (3251 GL/year, including measurement noise). This represents a 9 percent difference, or approximately 5 percent of the whole water balance. The uncertainty in losses and gains suggests an average uncertainty in water balance simulation of around 10 percent. There may be more internal model uncertainty in assumptions about runoff generation that are implicit in the river modelling methodology. Uncertainty associated with development – farm dam increases in particular –is estimated at less than 2 percent of average annual flow in the Goulburn River and less than 1 percent in the Broken River, which is small compared to other uncertainties.

5.4.3 Implications for use of these results

The model is able to reproduce observed streamflow patterns very well. It produces estimates of water balance terms that agrees with water balance accounts. The projected changes in flows due to climate change are greater than model noise under the dry and medium scenarios, but similar to model noise for the wet scenarios. The model provides strong evidence of changes in flow pattern due to development in the Goulburn River but not in the Broken River. The projected changes due to future development are very small (less than 2 percent) when compared to the projected changes under most of the climate change scenarios. Overall the model is well suited for the purpose of this project. Predictions of changes in low flows patterns are assigned a low level of confidence. This may be relevant to any assessments of the ecological impacts of hydrological changes.


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5.5 References

Bormann H (2005) Evaluation of hydrological models for scenario analyses: Signal-to-noise-ratio between scenario effects and model uncertainty. Advances in Geosciences 5, 43–48.

Bredehoeft J (2005) The conceptual model problem—surprise. Hydrogeology Journal 13, 37–46. DSE (2005) Goulburn Simulation Model – Calibration for the Murray Darling Basin Cap. Department of Sustainability and Environment,

Victoria, Melbourne. Water allocation, Water Sector Group. Funtowicz SO and Ravetz J (1990) Uncertainty and Quality in Science for Policy. Kluwer Academic Publishers, Dordrecht. MDBC (2006) Goulburn/Broken/Loddon and Campaspe Valleys-Independent Audit of Cap Model. Report prepared for the Murray-

Darling Basin Commission by Bewsher Consulting. Nash JE and Sutcliffe JV (1970) River flow forecasting through conceptual models, 1: a discussion of principles. Journal of Hydrology 10,

282–290. Pappenberger F and Beven KJ (2006) Ignorance is bliss: Or seven reasons not to use uncertainty analysis. Water Resources Research

42, W05302, doi 10.1029/2005WR004820. Refsgaard JC and Henriksen HJ (2004) Modelling guidelines–terminology and guiding principles. Advances in Water Resources 27, 71–

82. Refsgaard JC, van der Sluijs JP, Brown J and van der Keur P (2006) A Framework for dealing with uncertainty due to model structure

error. Advances in Water Resources 29, 1586–1597. SKM (2006) Goulburn Simulation Model – Update of Inputs 2006 report. Sinclair Knight Merz. Van der Sluijs JP, Craye M, Funtowicz S, Kloprogge P, Ravetz J and Risbey J (2005) Combining quantitative and qualitative measures

of uncertainty in model based environmental assessment: the NUSAP System. Risk Analysis 25, 481–492. Van Dijk AIJM et al. (2008) River model uncertainty assessment. A report to the Australian Government from the CSIRO Murray-Darling

Basin Sustainable Yields Project. CSIRO, Australia. In prep. Weiss C (2003) Expressing scientific uncertainty. Law, Probability and Risk 2, 25–46.


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6 Groundwater assessment This chapter describes the groundwater assessments for the Goulburn-Broken region. It has nine sections:

• a summary of key issues and messages • a description of the groundwater management units in the region • a description of surface–groundwater connectivity • an outline of the recharge modelling approach • an outline of the groundwater modelling approach • a presentation and description of modelling results • an assessment of water balances for lower priority groundwater management units • a presentation of conjunctive use indicators • a discussion of key findings.

6.1 Summary


There are six groundwater management units (GMUs) that cover part of the region. The area not covered by GMUs is known as ‘unincorporated’. A numerical groundwater model developed for this project underpins the assessment of four of the GMUs. Management intervention in response to watertable drawdown under future development was not included in the groundwater modelling, and this may act to reduce some of the predicted impacts. Simple water balance analyses were conducted on the remaining two GMUs.

6.1.2 Key messages

• Groundwater extraction in the Goulburn-Broken region for 2004/05 is estimated to be 92 GL. This represents 5.4 percent of groundwater use in the Murray Darling Basin (MDB). About 87 percent of this extraction came from the Shepparton GMU (which is a Water Supply Protection Area). This level of use represents 10 percent of current total water use on average and 16 percent in years of lowest surface water use.

• Surface–groundwater connectivity mapping indicates that the Goulburn River is gaining along most of its length, but losing over two small sections – upstream of the Goulburn Weir and downstream of Loch Garry. Broken Creek is losing at a moderate rate over most of its length. The Broken River is considered to be gaining at a high rate downstream of Orrvale.

• Current groundwater extraction is at a moderate (37 percent of recharge) level of development in the modelled Shepparton GMU and in the unmodelled Alexandra GMU. Current extraction is low in the modelled Kialla, Nagambie and Goorambat GMUs and in the unmodelled Kinglake GMU. Much of the pumping from the Shepparton GMU is sourced from reduced groundwater evapotranspiration – a significant fraction of the groundwater is pumped for salinity control and a reduction in evapotranspiration is the intended consequence.

• Historical groundwater extraction has and will continue to impact on streamflow in the rivers of the region. The total average impact will be an eventual loss of streamflow to groundwater of 20 GL/year with most of this occurring by 2010. Nearly 15 GL/year of this impact is associated with extraction from the modelled Southern Riverine Plains area, and the remainder is associated with extraction from unmodelled GMUs.

• The projected average groundwater extraction by 2030 is 154 GL/year. This is an increase of 67 percent over current levels. Most of the increase in groundwater extraction is expected to occur in the Shepparton GMU where extraction (under the best estimate 2030 climate) would then be 64 percent of recharge.

• Projected average groundwater extraction by 2030 would raise the level of development in the modelled Nagambie GMU and in the unmodelled Kinglake GMU from low to moderate. Extraction from the modelled Kialla and Goorambat GMUs would remain at low levels, while extraction from the unmodelled Alexandra GMU would increase to a high level.


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• The total eventual impact of groundwater extraction at projected 2030 levels would be an average streamflow reduction of 37 GL/year and 12 GL/year of this would be due to groundwater extraction outside of the modelled Southern Riverine Plains area.

6.1.3 Uncertainty

The priority of the GMU in the context of the project and the analysis method were ranked. Ideally the rankings match so that information on GMUs that is likely to influence MDB-wide outcomes is reliable.

The duration of the modelling was 222 years. Any models that (i) have not been previously calibrated under steady state conditions or (ii) have a small extent can be less than fit for the purpose of the project. If the first of these conditions is not met, the modelled watertable levels may show drifts that are more associated with the calibration process than hydrological processes. If the second condition is not met, the boundary conditions imposed on the model may overly affect the groundwater balance and lead to spurious results. A model may be fit for purpose (for this project) for assessing water availability at the larger scale but less than adequate for addressing local management issues.

The long model duration is required to bring the groundwater system to a ‘dynamic equilibrium’ (over the first 111 years). The second 111 years runs in sequence with surface water models to provide input to surface–groundwater interactions. Dynamic equilibrium may not be reached within 111 years in some cases. The most likely cause for dynamic equilibrium not being reached is that extraction exceeded recharge from all sources for the model area or for some components of the model area and the watertables gradually fell. Where this was the case, it indicates that the modelled pattern of pumping bores is not sustainable. In such cases, the modelling results will have implications for beyond the project and in particular for the sustainable extraction limit.

The assessment methods are ranked as: hydrogeological description – minimal; simple water balance – simple; and numerical modelling – medium to very thorough. The ranking of the numerical modelling is based on (i) the quality of monitoring data (length of period and spatial distribution); (ii) the quality of extraction data (metered versus estimated); (iii) complexity of process representation; (iv) availability of field data independent of calibration and (v) explicit representation of surface–groundwater connectivity and (vi) level of independent peer review. Since at least three of these criteria are based on availability or quality of data, a good calibration fit in line with the best modelling guidelines may still not rank well. Also, the more mature a model, the more opportunities there are for obtaining a higher ranking because of data availability and peer review. A very thorough model should provide very good reliability in addressing issues of groundwater balance and hence extraction limits.

The Southern Riverine Plain groundwater model used for assessment of higher priority GMUs in the catchment was developed for this project. It was peer-reviewed but it has not received widespread scrutiny. Lateral flows from outside the model area are small. The grid size is 1000 m, coarser than other models.

The model was assessed as thorough and is adequate for providing information on water availability in the context of this project. It is less reliable for local management requirements. The model reached a dynamic equilibrium under all scenarios. The level of reliability of predictions could be improved to ‘very thorough’ to recognise the importance of this groundwater resource. The simple water balances will have high uncertainty.

6.2 Groundwater management units

6.2.1 Location

The aquifers within the region are divided into a number of groundwater management units (GMUs) which are three-dimensional in nature, allowing for the layered nature of geological formations at different depths. The GMUs relevant to the region are:

• Alexandra Groundwater Management Area (V11) • Kinglake Groundwater Management Area (V12) • Goorombat Groundwater Management Area (V38) • Nagambie Groundwater Management Area (V41)


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• Parts of Kialla Groundwater Management Area (V40) • Shepparton Water Supply Protection Area (V43) • Campaspe Deep Lead Water Supply Protection Area (V42) • Katunga Water Supply Protection Area (V39).

For ease of reference, the various Groundwater Management Areas (GMA) and Water Supply Protection Areas (WSPA) are simply referred to as GMUs. Where the term WSPA occurs in the body of this report, it refers to regulatory matters not the groundwater assessment. Only the first six GMUs are assessed in this report. The Campaspe Deep Lead and Katunga GMUs are mostly located within the Campaspe and Murray regions respectively, and are assessed in the reports for those regions. The GMUs do not cover the entire region, and those areas not covered are referred to as ‘unincorporated areas’. The locations of these GMUs are shown in Figure 6-1.

Figure 6-1. Location of groundwater management units in the region


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6.2.2 Ranking

Table 6-1 shows the GMU priority and assessment rankings for this project. The priority ranking focuses efforts on the GMUs that affect the overall groundwater or surface water resource in the MDB.

The ranking ranges from ‘very low’ to ‘very high’ in the context of this project and is based on the level of groundwater use, potential for growth in use and the potential for groundwater to impact on streamflow.

The groundwater assessments vary for different GMUs reflecting the availability of data and analysis tools as well as the priority of the GMU. Assessment rankings range from minimal to very thorough. A simple ranking denotes a simple water balance approach while thorough denotes application of a calibrated and reviewed numerical groundwater model, perhaps not supported by good historical data nor as widely peer reviewed as the best models. A high priority ranked GMU could expect to have a high level of assessment. A mismatch highlights where the level of assessment is inconsistent with its priority ranking.

The analysis method is consistent with the priority ranking for the GMUs listed in Table 6-1. Despite their low to very low priority, Goorombat, Kialla and Nagambie GMUs are covered by the Southern Riverine Plains groundwater model and so underwent a relatively high level of assessment. Shepparton GMU has a medium priority and is also covered by the Southern Riverine Plains groundwater model. The assessments for Alexandra and Kinglake GMUs were limited to a simple analysis by providing an overview of the hydrogeological setting including surface–groundwater connectivity and an evaluation of the impact of changing rainfall recharge and extraction under each of the scenarios. While these limited assessments are appropriate within the constraints and for the terms of reference of this project, additional work may be required for local management of groundwater.

The main groundwater indicator used is the ratio of extraction to rainfall recharge (E/R). This is used to indicate the level of groundwater development under the classifications: low (0.0–0.3), medium (0.3–0.7), high (0.7–1.0) and very high (>1.0). Streams can contribute to recharge in alluvial GMUs and groundwater extraction can induce further recharge. The impact of groundwater extraction on streamflow is also assessed.

Table 6-1. Groundwater entitlements and current and future extractions for Goulburn-Broken region

Code Name Priority ranking Assessment ranking

Total entitlement

Current extraction(1) (2004/05)

Permissible Consumptive

Volume

Estimated use (2030)

GL/y V11 Alexandra GMA low simple 1.71 0.70 1.9 1.52V12 Kinglake GMA(2) very low simple 1.49 1.05 3.8 1.74V38 Goorambat GMA very low thorough 1.54 0.48 4.9 0.852V40 Kialla GMA low thorough 2.33 0.86 2.8 0.854V41 Nagambie GMA low thorough 6.65 4.55 5.7 4.55V43 Shepparton WSPA(3) medium thorough 203.6 80.65 none set 136.6- Unincorporated Areas(4) - 7.87 3.90 none set 8.23(1) Current extraction volumes have been supplied by the Victorian Department of Sustainability and Environment, and include estimates of stock and domestic use of 0.10 GL/year for Alexandra, 0.53 GL/year for Kinglake, 0.03 GL/year for Goorambat, 0.05 GL/year for Kialla, 0.14 GL/year Nagambie, 0.83 GL/year for Shepparton and 0.36 GL/year for unincorporated areas. (2) Approximately 78% of the Kinglake GMU falls within the Goulburn Basin. Groundwater entitlements and use are for this portion of the GMU only as the remainder lies outside the MDB. (3) Approximately 80% of the Shepparton WSPA is contained within the region. Entitlement and Extraction values are reported for the whole GMU. (4) Figures for the unincorporated areas relate to areas of fair groundwater quality (< 1500 mg/L Total Dissolved Solids (TDS)) in the upper part of the catchment.

6.2.3 Hydrogeology

Fractured rock aquifers dominate the highlands of the region. Local groundwater flow systems occur in areas with greater relief and steeper slopes and they respond rapidly to seasonal variations in rainfall. Intermediate groundwater flow systems operate where the landscape is weathered and relief more subdued. Groundwater quality is good due to rapid recharge and higher rainfall but groundwater yields are lower than the unconsolidated sediments of the alluvial flats.


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Alluvial sediments are deposited by rivers flowing north from the highlands. The Renmark and Calivil Formations are the deepest of the sedimentary aquifers in the region and comprise fluvial clays, silts, sands and gravels. The two formations are often hydraulically connected.

The sediments are thickest in palaeovalleys extending north from the highlands, where they are referred to as ‘deep leads’. The deep leads broaden towards the north and merge to form a continuous sheet under much of the south-eastern MDB. Coarse sands and gravels allow hydraulic conductivities as high as 200 m/day. Salinities in the Renmark and Calivil Formations are generally fresher than the overlying aquifer system, mostly ranging from 300 mg/L TDS to 2,000 mg/L TDS to 7,000 mg/L TDS in some areas.

The Shepparton Formation is the uppermost aquifer system in the alluvial sequence and comprises fluvio-lacustrine silts, sands and clays. Hydraulic conductivities are as much as 30 m/day in the coarsest units. They are significantly lower in finer grained sediments and may promote downward leakage into the underlying Calivil and Renmark Formations. Groundwater salinity ranges from 1,000 mg/L TDS to more than 20,000 mg/L TDS.

Trends in water levels

Groundwater levels in the highlands have tended to follow the annual average rainfall since records began in the 1980s. A decrease in annual average rainfall, along with increased groundwater extraction in some areas, has seen groundwater levels decline 2 to 3 m since 1996 (Figure 6-2).

300

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305

1982 1986 1990 1994 1998 2002 2006 2010

RSW

L (m

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D)

Figure 6-2. Hydrograph for Bore 118893 completed in the fractured rock aquifer of the Goulburn-Broken highlands showing a declining trend in water level. Ground level is 312.27 m AHD.

Hydrographs from the Renmark Formation show the combined effects of a dry climatic period and increased groundwater extraction displaying falls in groundwater levels of up to 10 m from the year 2000 to 2005 (Figure 6-3).

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1982 1986 1990 1994 1998 2002 2006 2010

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Figure 6-3. Hydrograph for Bore 88009 completed in the Renmark Group displaying a falling trend of up to 10m. Ground level is 99.8 m AHD.


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Hydrographs from the Calivil Formation In the Broken Catchment display a rising trend of approximately 10 m since 1986 associated with clearing of native vegetation (Figure 6-4). Prior to 1986 clearing of native vegetation across the MDB resulted in high groundwater levels and high saline groundwater discharge to surface water.

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100

105

1982 1986 1990 1994 1998 2002 2006 2010

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L (m

AH

D)

Figure 6-4. Hydrograph for Bore 60074 completed in the highland valley Deep Lead Calivil Formation showing a rise in groundwater level. Ground level is 140.00 m AHD.

Hydrographs in the Calivil Formation in the Goulburn Catchment display declines in water level since the early 2000s associated with increased groundwater extraction and a drier climate (Figure 6-5).

106

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1982 1986 1990 1994 1998 2002 2006 2010

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L (m

AH

D)

Figure 6-5. Hydrograph for Bore 46190 completed in the Deep Lead of the Calivil Formation in the Goulburn Catchment displaying a falling trend since the early 2000s. Ground level is 119.88 m AHD.

Groundwater levels in the Shepparton Formation display a similar downward trend with hydrographs indicating that the Shepparton Formation also receives recharge from flooding as well as rainfall (Figure 6-6). The downward trend is a consequence of the management plan for the Shepparton irrigation region that sponsors lowering of the watertable in order to reduce the salinity risk.


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120

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1982 1986 1990 1994 1998 2002 2006 2010R

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(m A

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)

Figure 6-6. Hydrograph for Bore 109763 displaying rapid rises in water level consistent with flood recharge. Ground level is 128.17 m AHD.

6.3 Surface–groundwater connectivity

The objectives of the surface–groundwater connectivity mapping are to (i) provide a catchment context for groundwater–surface water interactions (ii) constrain surface water balance and (iii) constrain groundwater balances.

The main output of this task is a map of groundwater fluxes (magnitude and direction) adjacent to main streams. The approach uses Darcy’s Law and hence estimates the groundwater flux to the stream as the product of the aquifer hydraulic conductivity, aquifer thickness and groundwater gradient adjacent to the stream. The method is dependent on the availability of appropriate groundwater monitoring and on previous work estimating hydraulic conductivity.

River levels and groundwater levels were compared at a single point in time to provide a snapshot of the direction and magnitude of the flow between surface water and groundwater. The date selected for production of the flux map and associated calculations was February 2006 as this was the most recent date with a large quantity of both bore and river elevation data available.

An average aquifer thickness of 40 m was used for all river reaches in the lower catchment. An estimated saturated aquifer thickness of 20 m was used in the mid catchment and also in the highlands where the fractured rock aquifers become more prevalent. The adopted hydraulic conductivity values varied across the region between 3 and 25 m/day. A value of 5 m/day was used for the entire length of Broken Creek and for the Goulburn River downstream of Murchison. A value of 25 m/day was used for the Broken River between the junction with the Goulburn River and Gowangardie. A hydraulic conductivity of 3 m/day was used upstream of both Murchison and Gowangardie.

No flux calculations were undertaken for the fractured rock aquifers upstream of Trawool on the Goulburn River (stream gauge 405201) and upstream of the Lake Mokoan Diversion Weir on the Broken River (stream gauge 404226) due to the lack of bore data.

Figure 6-7 shows the surface–groundwater connectivity results from the flux assessment. The Goulburn River is assumed to be gaining in the upper part of its catchment (upstream of Trawool) but there is an absence of bore data in this area, and so the classification is of low reliability. The assessment found that:

• The Goulburn River is gaining at a low rate between Trawool and the confluence with Hughes Creek. The river loses water at a low rate for approximately 35km downstream of the junction with Hughes Creek where it becomes hydraulically neutral. The losing conditions are likely to be due to groundwater development.

• The Goulburn River downstream of Murchison was gaining at a moderate rate for approximately 90km to Loch Garry. The Goulburn River for approximately 50km downstream from Loch Garry is losing at a low rate, after which it changes to low gaining to the junction with the Murray River.

• The Broken River is gaining for the 30 km reach downstream of Lake Nillahcootie although there is a lack of bore data. The Broken River between the Lake Mokoan diversion weir and Casey Weir is losing at a low rate. The river Below Casey Weir is hydraulically neutral until approximately 12 km upstream of Stream Gauge 404222. Downstream of this point the river gains at a high rate to the junction with the Goulburn River.


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• Broken Creek was found to be moderately losing (-0.25 to -0.41 ML/day/km) over most of its length (from the junction with the Broken River to Nathalia Town Weir), but is hydraulically neutral close to the junction with the Murray River.

Comparisons were made between river levels at two gauging stations and adjacent groundwater levels to obtain information on how these fluxes change with time. Bore levels were adjusted to account for changes in river level between the gauging station and the river adjacent to the bore since groundwater bores are rarely located immediately adjacent to gauging stations. The analysis showed a trend for gaining sections of the river to reduce the rate of gain. The relationship between groundwater level and river stage for a gaining section of the Broken River (near Orrvale, Stream Gauge 404222) is shown in Figure 6-8. The ongoing drawdown from groundwater extraction decreases the gradient from the aquifer to the stream.

Figure 6-7. Map of surface–groundwater connectivity


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1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

Elev

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AH

D)

Broken River - gauge 404222Bore 2138 (+0.5 m elevation shift)Bore 2184 (+0.5 m elevation shift)

Figure 6-8. Comparison of Broken River level at Orrvale, with groundwater levels in two nearby bores. Since bores are located approximately 400 m downstream of the gauging station, levels have been uniformly increased by 0.5 m to account for changes in river

level between the gauging station and the river adjacent to the bores.

6.4 Recharge modelling

Recharge Scaling Factors (RSFs) are applied in the groundwater modelling and in the simple water balance analyses. Values of diffuse dryland recharge are used to calibrate the original implementation of the groundwater model and for management of the other GMUs within the region. The RSFs are used to multiply these values to provide estimates of dryland recharge under different climate scenarios to be used in further analyses. The RSF is 1.0 by definition for Scenario A and close to 1.0 for other scenarios. The impacts of climate change on recharge are reported as percentage changes from Scenario A. The RSFs are obtained by dividing the percentage change by 100 and adding to 1.0. RSFs are not applied to irrigation recharge, which is likely to be less affected by climate change, and hence considered to be constant under the different climate scenarios.

Scenarios Cdry, Cmid and Cwet represent a range of global climate model (GCM) output, selected based on a ranking of mean annual runoff (Chapter 3). Groundwater recharge is not perfectly correlated with mean annual rainfall or runoff. Apart from mean rainfall, diffuse dryland recharge is sensitive to seasonal rainfall and potential evaporation and to the extreme events or years that lead to episodic recharge. In semi-arid to sub-humid areas extreme events become more important. A number of GCMs show an increase in extreme events (leading to more recharge), but the scenario variants are selected based on mean annual runoff which is more dependent on average and seasonal rainfall.

Recharge also depends on the land use and soils. These can be locally variable and reflect local spatial variation in RSFs. An estimate for a small GMU will be sensitive to these local variations, while in larger areas with a broader range of soils and land uses the estimates will be more robust. RSFs were estimated for all 15 GCMs under Scenario C.

In all cases, a one dimensional soil-vegetation-atmosphere water transfer model (WAVES; Zhang and Dawes, 1998) was used for selected points around the MDB for combinations of soils and vegetation. Spatial data on climate, vegetation and soils were then used to interpolate values to regions.


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Figure 6-9 shows the percentage change in the modelled mean annual recharge averaged over the region for Scenario C relative to Scenario A for the 45 scenarios (15 GCMs for each of the high, medium and low global warming scenarios). The percentage change in the mean annual recharge and the percentage change in mean annual rainfall from the corresponding GCMs are tabulated in Table 6-2. The plots show that there is a wide range in results across GCMs and scenarios for the region with just over half the scenarios predicting less recharge and the remainder predicting more recharge. The high global warming scenario predicts both the highest and lowest change in recharge for the region.

Of the 45 climate change scenarios, only scenarios Cdry, Cmid and Cwet are shown in subsequent modelling and reporting. These variants are based on the runoff modelling and are indicated in Table 6-2 in bold type. The choice of GCMs for surface runoff is comparable to those that would be chosen if recharge formed the basis of choice with the second highest, second lowest and median in surface run-off being respectively the second highest, sixth lowest and the median for RSF. The large variability in RSFs is related to the large variability in rainfall produced by the various GCMs. Rainfall and RSFs are correlated, but not perfectly. Some GCMs that indicate reductions in rainfall lead to RSFs greater than 1.0. This is due to the more extreme events being more frequent, in spite of a reduction in mean rainfall.

-60%

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giss

_aom ipsl

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a_t4

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Cha

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in m

ean

annu

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nt) High global warming

Medium global warmingLow global warming

Figure 6-9. Percentage change in mean annual recharge from the 45 Scenario C simulations (15 GCMs and three global warming scenarios) relative to Scenario A recharge


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Table 6-2. Summary results from the 45 Scenario C simulations. Numbers show percentage change in mean annual rainfall and recharge under Scenario C relative to Scenario A. Those in bold type have been selected for further modelling.

High global warming Medium global warming Low global warming GCM Rainfall Recharge GCM Rainfall Recharge GCM Rainfall Recharge

giss_aom -22% -36% giss_aom -14% -25% cnrm -5% -12%ipsl -19% -30% ipsl -12% -20% giss_aom -6% -11%miroc -7% -23% cnrm -12% -19% ipsl -5% -9%cnrm -18% -22% miroc -5% -12% mpi -2% -5%csiro -10% -13% csiro -6% -9% csiro -3% -4%inmcm -6% -13% inmcm -4% -9% inmcm -2% -4%iap -2% -9% mri -4% -6% miroc -2% -3%miub 0% -9% iap -2% -6% mri -2% -3%mri -6% -9% miub 0% -5% iap -1% -2%mpi -6% -7% mpi -4% -5% gfdl -3% -2%gfdl -9% -4% gfdl -6% -4% miub 0% -1%ncar_ccsm 0% -1% ncar_ccsm 0% -1% ncar_ccsm 0% 0%Ncar_pcm 2% 3% ncar_pcm 1% 4% ncar_pcm 1% 4%cccma_t63 0% 6% cccma_t47 0% 9% cccma_t63 0% 5%cccma_t47 0% 13% cccma_t63 0% 9% cccma_t47 0% 7%

6.5 Groundwater modelling

Groundwater extraction in the Shepparton, Goorombat, Nagambie and Kialla GMUs was analysed using the Southern Riverine Plains model. It was developed specifically for this assessment and covers a 292 x 250 km area spanning either side of the Murray River between Yarrawonga and Swan Hill. The model covers major parts of the Loddon River, Campaspe River, Goulburn River, Broken River, Wakool River, Edward River and Billabong Creek catchments.

6.5.1 Modelling approach

The groundwater model covers an area of 34,285 km2 and utilises a 1 km2 grid cell resolution. Outcropping bedrock forms the southern boundary of the active model domain and the northern boundary is defined by Billabong Creek. The groundwater model is divided into five layers based on the area’s hydrogeology: Upper Shepparton Formation, Lower Shepparton Formation, Calivil Formation, Renmark Group and bedrock (inactivated in the model). The distinction between the Upper and Lower Shepparton is arbitrary as the formation is extremely variable in character. Inclusion of two model layers to represent the Shepparton Formation allows additional flexibility in modelling vertical fluxes from the surface to the deep lead aquifers and enables the inclusion of aquitards if necessary above the Calivil Formation. Importantly the Southern Riverine Plains groundwater model combines the Lower Murray, Katunga and Campaspe models and attempts to break down the controlling influence of model boundary conditions and provide an enhanced representation of intermediate and regional scale interference patterns.

Only the main stems of major rivers are included in the model. A number of drainage areas were included in the model to help account for tributaries and drainage channels that cannot be explicitly modelled. Drainage cells were only placed in areas that are prone to shallow water tables and are designed to mimic natural or manmade drainage features that would act to intercept rising watertables. These are particularly common in the irrigated areas of NSW.

Dryland rainfall recharge and irrigation recharge are both incorporated into the model. River recharge can also occur where river levels are higher than adjacent groundwater levels. The MODFLOW groundwater evapotranspiration package is used to simulate evapotranspiration from shallow water tables. Groundwater pumping is simulated from a total of 2400 extraction bores. The model was calibrated for the period January 1990 to December 2005. The mass balance for the modelled area is shown in Figure 6-10.


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Inflows

25%

48%

20%

7%

StorageRechargeRiver leakageLateral flowExtractionDrainsEvapotranspiration

Outflows

24%

17%

6%30%

6%

17%

Figure 6-10. Mass balance for the calibration model for the model area (Jan 1990 – Dec 2005; Inflows = Outflows)

6.5.2 Scenario implementation

The objective of the numerical modelling is to assess groundwater and surface water impacts under a range of groundwater extraction scenarios. The groundwater impacts are characterised by resource condition indicators and the surface water impacts are characterised by river losses to groundwater. Under Scenario A, groundwater extraction was 25 GL/year for the portion of the model contained within the region, and 245 GL/year across the model area.

Climate can change dryland recharge, the area of irrigation or river flows. The impact of climate on diffuse dryland recharge is assessed through the application of a RSF (Section 6.4). However, RSFs were not varied spatially across the model area, which includes four reporting regions. Constant scaling factors were used across the entire model for each of the scenarios, instead.

Table 6-3 shows the percentage changes in recharge rate under scenarios B and C. Scenario B represents a continuation of current drought conditions, while Scenario C represents the climate as predicted for 2030 by the GCMs. Scenario D also represents the climate as predicted for 2030 by the GCMs and has the same three variants as Scenario C, with the same dryland recharge rates.

Scenario D introduces changes in water management such as: changes in groundwater use, an increase in tree cover and more farm dams. River stage (which is calculated from outputs of the REALM model) may vary from Scenario C because of change to water management. Groundwater pumping was increased to a total of 44 GL/year for Scenario D in the Goulburn-Broken section of the model and 300 GL/year across the model domain. This level of pumping is consistent with the likely future maximum pumping as defined by the New South Wales and Victorian governments.

Table 6-3. Change in recharge applied to model scenarios under scenarios B and C

B Cdry Cmid Cwet -25% -34% -3% +14%

The river and groundwater models are run in a sequence to simulate the effect of climate on surface–groundwater exchange fluxes and both groundwater and surface water balances (Chapter 1). The REALM river model implicitly includes surface–groundwater exchanges within the unattributed losses and gains (which is the difference between gauged flows that cannot be attributed to diversions). The calibration periods for the groundwater and surface water models broadly coincide. Hence the change in surface–groundwater exchange fluxes in the MODFLOW outputs from the calibration period is assumed to be the same as the change in groundwater gains and losses from that included in the unattributed gains and losses. Extraction rates were assumed to be constant in all cases.

Model results are expressed in terms of water levels, changes to the groundwater balance, and in terms of a number of groundwater indicators that are defined in Table 6-4.


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The environmental groundwater indicator was calculated using annual total recharge from all sources and may include diffuse rainfall and irrigation recharge, river leakage, leakage from overlying aquifers and lateral flow from outside GMU boundaries.

Table 6-4. Definition of groundwater indicators

Groundwater Indicators Security indicator Percentage of years in which extraction is less than the average recharge over the previous ten-year

period. Values less than 100 indicate increasing risk of sustained long-term groundwater depletion and thus a lower security of the groundwater resource.

Environmental indicator Ratio of average annual extraction to average annual recharge. Values of more than 1.0 indicate a long-term depletion of the groundwater resource and consequential long-term environmental impacts.

Drought indicator Difference in groundwater level (in metres) between the lowest level during each 111-year scenario simulation and the mean level under Scenario A. This is a relative indicator of the maximum drawdown under each scenario.

Conjunctive use indicator Percentage of years in which groundwater extraction is more than 50 percent of the total water use in the region. This indicates the relative importance of groundwater compared with surface water for the region.


The Southern Riverine groundwater model covers the northern half of the region. The southern half is dominated by the outcropping bedrock formations of the Great Dividing Range and so has limited groundwater availability. The results highlight some of the complexities of regions that do not have hydrogeological boundaries. Table 6-5 (and Figure 6-11 and Figure 6-12) shows how the lateral groundwater flow out of the region increases in scenarios with higher pumping. This results from the increases in pumping in surrounding regions, specifically the enhanced drawdown cone centred near Deniliquin. There are large increases in net river loss and decreases in evapotranspiration in response. The result reinforces the need for assessment of the southern riverine plain with a single groundwater model. A stand-alone groundwater model for this area would show increased fluxes into the model in response to long-term pumping. The modelling results illustrate the opposite (that is, a reduction in fluxes into the area) due to greater drawdown in neighbouring areas when considered in the correct setting of numerous productive aquifers interacting within a continuum. Differences in groundwater pumping between scenarios A, B and C, and between the different D scenarios are due to some model cells running dry, with consequent loss of pumping. Thus, for example, Scenario Ddry has slightly less groundwater pumping than Scenario Dwet, because the reduction in recharge in the former case causes some additional model cells to dry up. The effects of climate change are pronounced in this southern area. Scenarios Cdry and Ddry cause significant reductions in rainfall recharge. This has significant follow-on impacts for stream–aquifer interactions and evapotranspiration. Groundwater pumping increases total net river losses to groundwater from 14.8 GL/year under the without-development scenario to 29.4 GL/year under Scenario A. This will increase to 46.8 GL/year under Scenario Ddry. The total river losses to groundwater exceed the groundwater pumping under most of the scenarios. Flow across the head-dependent boundary reflects water movement between the deep lead aquifers and the basement.


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Table 6-5. Groundwater balance for the area of the Goulburn-Broken region covered by the Southern Riverine groundwater model under without-development scenario and scenarios A, B, C and D

Groundwater balance Without-development

A B Cdry Cmid Cwet Ddry Dmid Dwet

GL/y Inflows Total diffuse recharge 111.0 110.8 94.9 89.3 108.9 119.5 88.9 108.5 119.4Head dependent boundary 0.0 0.1 0.2 0.3 0.1 0.1 1.1 0.6 0.5River recharge to groundwater 45.6 51.9 44.5 45.0 48.5 49.4 56.6 58.0 57.8Lateral flow 36.8 32.6 32.0 31.7 32.5 32.9 30.7 31.2 31.5Total 193.4 195.4 171.6 166.3 190.0 201.9 177.3 198.3 209.2Outflows Groundwater pumping 0.0 24.9 24.8 24.7 24.9 24.9 41.2 42.9 43.7Head dependent boundaries 3.1 2.3 1.6 1.4 2.2 2.5 1.1 1.7 2.1Lateral flow 56.4 70.3 70.1 70.3 70.3 70.4 76.7 75.5 75.0Evapotranspiration 95.3 71.3 59.4 56.1 69.1 76.1 48.0 59.2 65.3To drains 7.7 4.0 2.7 2.2 3.9 4.8 0.8 1.6 2.3To rivers 30.8 22.5 13.1 11.7 19.6 22.9 9.8 17.4 20.6Total 193.3 195.3 171.7 166.4 190.0 201.6 177.6 198.3 209.0Net river losses to groundwater 14.8 29.4 31.4 33.3 28.9 26.5 46.8 40.6 37.2

0

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40

60

80

100

120

140

Total diffuserecharge

Headdependentboundary

Riverrecharge togroundwater

Lateral flow

Aver

age

flux

(GL/

y)

C range D range ACmid Dmid B

Figure 6-11. Groundwater inflows to the Goulburn-Broken region under scenarios A, B, C and D


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0

10

20

30

40

50

60

70

80

90

Groundwaterpumping

Head dependentboundaries

Lateral flow Evapotranspiration To drains To rivers

Aver

age

flux

(GL/

y)

C range D range A

Cmid Dmid B

Figure 6-12. Groundwater outflows from the Goulburn-Broken region under scenarios A, B, C and D

6.6.1 Shepparton GMU

The Shepparton GMU is a WSPA that comprises the shallow aquifers of the Shepparton Formation, overlying the Katunga GMU, and parts of the Campaspe GMU, Kialla GMU and Mid-Goulburn GMU. Eleven observation bores were selected to provide a spatial coverage across the GMU and to indicate the water level changes under the scenarios in both the Upper and Lower Shepparton Formation aquifers. Table 6-6 shows effect of the various scenarios on the mean groundwater water levels. Groundwater levels under the various climate change scenarios vary from 0.28 m higher to 5.21 m lower than under Scenario A.

Table 6-6. Median groundwater level under Scenario A, and changes from this level under scenarios B, C and D

Median groundwater level changes A B Cdry Cmid Cwet Ddry Dmid Dwet m AHD change from Scenario A (m) Layer 1 102.34 -0.61 -0.87 -0.08 0.25 -7.16 -5.04 -4.28Layer 2 96.82 -0.84 -1.19 -0.13 0.32 -3.27 -1.77 -1.74Average 99.58 -0.12 -1.03 -0.1 0.28 -5.21 -3.4 -3.01

The water balance of the WSPA is characterised by large volumes of diffuse recharge (mainly from irrigation) and high levels of groundwater pumping, mostly for the control of shallow watertables (Table 6-7, Figure 6-13 and Figure 6-14).

A comparison of the without-development scenario and Scenario A shows an increase in groundwater flowing out of the WSPA when pumping is introduced despite the high levels of groundwater pumping in the WSPA. This is because of the high levels of pumping in the surrounding GMUs (most notably the Katunga, Campaspe and Lower Murray GMUs). There is also a decrease in groundwater evapotranspiration because of groundwater pumping under Scenario A as a consequence of the large reduction in area of shallow watertables. Reduction in evapotranspiration accounts for approximately 71 percent (50 GL/year) of pumping. Such a reduction is likely to have a positive benefit in terms of alleviating dryland salinity in affected areas.


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Table 6-7. Average annual water balance for the Shepparton GMU under scenarios A, B, C and D



GL/y Inflows Total diffuse recharge 185.4 185.3 164.3 156.8 182.8 197.0 156.5 182.5 196.8Head dependent boundary 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0River recharge to groundwater 55.8 66.6 57.7 57.2 62.5 64.2 69.1 72.8 73.3Lateral flow 17.4 16.2 15.4 14.9 16.0 16.5 14.8 16.1 16.6Total 258.6 268.1 237.4 228.9 261.3 277.7 240.4 271.4 286.7Outflows Groundwater pumping 0.0 69.4 69.2 68.8 69.4 69.4 110.7 116.8 119.6Head dependent boundaries 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Lateral flow 41.8 69.6 69.1 69.1 69.5 69.8 63.9 65.4 66.2Evapotranspiration 132.6 83.1 68.0 63.4 80.1 89.3 51.4 64.6 71.7To drains 46.7 19.5 14.3 12.5 18.9 22.3 1.4 3.4 5.1To rivers 37.5 26.3 16.7 15.3 23.3 26.8 12.9 20.6 24.1Total 258.6 267.9 237.3 229.1 261.2 277.6 240.3 270.8 286.7Note: Approximately 80 percent of the Shepparton WSPA is contained within the region, although the water balance is reported for the whole GMU.

0

50

100

150

200

250

Total diffuserecharge

Headdependentboundary

Riverrecharge togroundwater

Lateral flow

Aver

age

flux

(GL/

y)

C range D range ACmid Dmid B

Figure 6-13. Groundwater inflows into the Shepparton GMU under scenarios A, B, C and D


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20

40

60

80

100

120

140

Groundwaterpumping

Head dependentboundaries

Lateral flow Evapotranspiration To drains To rivers

Aver

age

flux

(GL/

y)C range D range ACmid Dmid B

Figure 6-14. Groundwater outflows from the Shepparton GMU under scenarios A, B, C and D

The groundwater indicators for the Shepparton GMU are listed in Table 6-8. The results show that groundwater security is high under all scenarios. The environmental indicator is 0.37 under Scenario A, but increases to 0.71 under Scenario Ddry. An increase in this value towards 1 represents a decrease of water for environmental purposes.

Scenario D shows large drawdown values in the indicator bores in the area of major groundwater extraction with falls of up to 30 m relative to the mean water level in Scenario A. This large drawdown is largely a consequence of the increase in groundwater extraction simulated under this scenario. Water within the Shepparton Formation aquifers does not form a major groundwater resource and much of the pumping is for salinity control. The increase in extraction simulated under Scenario D may not be appropriate for this area. Although the model increased groundwater pumping for irrigation and for salinity control under Scenario D, irrigation rates were not increased, and so the drawdown in the upper aquifer is considered to be an overestimate. Drawdowns ranged between 0.56 and 2.56 m under Scenario C, averaging 1.57 m. Drawdown within this layer may affect discharge to rivers and will also affect leakage to underlying aquifers both of which constitute major water resources. This level of drawdown would not occur in reality as groundwater pumping for salinity control would likely be reduced as the groundwater level declined.


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Table 6-8. Groundwater indicators for the Shepparton GMU under scenarios A, B, C and D


Security indicator percent 100% 100% 100% 100% 100% 100% 100% 100%Environmental indicator ratio 0.37 0.42 0.44 0.38 0.35 0.71 0.64 0.61Drought indicator metres Average -0.62 -1.28 -1.57 -0.71 -0.36 -5.94 -4.40 -3.91Observation bore

46195_1 -0.92 -1.30 -1.42 -0.98 -0.76 -1.79 -1.30 -1.0747253_1 -0.80 -1.23 -1.42 -0.85 -0.64 -7.38 -5.55 -4.7848282_1 -0.40 -0.93 -1.37 -0.44 -0.23 -30.00 -26.16 -24.8551001_1 -0.38 -0.87 -1.12 -0.44 -0.23 -1.19 -0.52 -0.2853672_1 -0.24 -1.04 -1.33 -0.34 0.28 -1.66 -0.65 -0.0956424_1 -0.73 -1.82 -2.21 -0.92 -0.36 -2.89 -1.53 -0.8762036_1 -0.70 -1.33 -1.59 -0.79 -0.45 -4.52 -3.01 -2.1897120_1 -0.89 -1.23 -1.43 -0.93 -0.75 -9.93 -6.92 -5.8697613_1 -0.55 -1.01 -1.34 -0.59 -0.41 -23.51 -18.18 -15.50105701_1 -0.16 -0.44 -0.56 -0.21 -0.12 -1.70 -0.67 -0.39110943_1 -0.34 -1.13 -1.46 -0.43 0.02 -3.62 -2.48 -1.9646195_2 -0.92 -1.30 -1.42 -0.98 -0.76 -1.79 -1.30 -1.0747253_2 -1.05 -1.81 -2.13 -1.17 -0.76 -5.25 -3.61 -2.9048282_2 -0.73 -1.47 -1.82 -0.84 -0.51 -5.25 -6.58 -7.8951001_2 -1.50 -2.31 -2.56 -1.67 -1.25 -2.34 -1.58 -1.1053672_2 -0.36 -1.60 -2.07 -0.51 0.31 -3.09 -1.45 -0.6256424_2 -1.06 -2.08 -2.44 -1.24 -0.72 -3.07 -1.82 -1.2062036_2 -1.05 -1.86 -2.18 -1.18 -0.76 -3.88 -2.49 -1.8297120_2 -0.93 -1.73 -2.12 -1.04 -0.62 -5.96 -3.67 -2.7897613_2 -0.69 -1.43 -1.78 -0.80 -0.46 -11.54 -8.91 -7.58105701_2 -0.82 -1.52 -1.78 -0.95 -0.62 -2.94 -1.86 -1.38110943_2 -0.92 -1.60 -1.90 -1.01 -0.66 -5.56 -4.47 -3.91

6.6.2 Goorambat GMU

The Goorambat GMU represents a small area of the entire model so the following water balance results should only be considered as a guide. Observation bore 65846 was selected to indicate the water level changes under the scenarios in both the Upper and Lower Shepparton Formation aquifers. Modelled groundwater levels are reported for both aquifers at this location even though this bore only screened within the Upper Shepparton. Table 6-9 shows the effect of the various scenarios on the mean groundwater levels. Groundwater levels under the various climate change scenarios vary from 0.06 m higher to 0.35 m lower than under Scenario A.

Table 6-9. Groundwater level in the Goorambat GMU under Scenario A, and changes from this level under scenarios B, C, D

Median groundwater level changes A B Cdry Cmid Cwet Ddry Dmid Dwet m AHD change from Scenario A (m) Upper Shepparton 152.47 -0.14 -0.18 -0.02 0.06 -0.34 -0.17 -0.08Lower Shepparton 152.47 -0.15 -0.19 -0.02 0.06 -0.37 -0.19 -0.10Average 152.47 -0.15 -0.19 -0.02 0.06 -0.35 -0.18 -0.09


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The impacts of climate on the water balance are pronounced and there are reductions in diffuse recharge of up to 30 percent under scenarios B, Cdry and Ddry. River recharge to groundwater increases as a consequence by up to approximately 30 percent, and groundwater discharge to rivers decreases by up to 50 percent (Table 6-10).

Table 6-10. Average annual water balance in the Goorambat GMU under scenarios A, B, C and D



GL/y Inflows Total diffuse recharge 1.6 1.6 1.2 1.1 1.6 1.9 1.1 1.6 1.9Head dependent boundary 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0River recharge 0.7 0.9 1.0 1.1 0.9 0.8 1.2 1.0 0.9Lateral flow 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1Total 2.4 2.6 2.3 2.3 2.6 2.8 2.4 2.7 2.9Outflows Groundwater pumping 0.0 0.3 0.3 0.3 0.3 0.3 0.4 0.4 0.4Head dependent boundaries 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Lateral flow 0.9 0.9 0.9 0.9 0.9 1.0 0.9 0.9 1.0To rivers 0.5 0.4 0.3 0.2 0.4 0.5 0.2 0.4 0.4Total 1.4 1.6 1.5 1.4 1.6 1.8 1.5 1.7 1.8

The groundwater indicators for Goorombat GMU are listed in Table 6-11. The results show that groundwater security is high under all scenarios. The environmental indicator is 0.09 under Scenario A, and increases only to 0.16 under Scenario Ddry. An increase in this value towards 1 represents a decrease of water for environmental purposes. The relatively low values of this indicator reflect the relatively low rate of groundwater pumping within this GMU. Drawdowns (reflected by the drought indicator) are also relatively modest and range between 0.33 m under Scenario A and 0.69 m under Scenario Ddry.

Table 6-11. Groundwater indicators for the Goorombat GMU under scenarios A, B, C and D


Security indicator percent 100% 100% 100% 100% 100% 100% 100% 100%Environmental indicator ratio 0.09 0.11 0.11 0.10 0.09 0.16 0.14 0.12Drought indicator m Average -0.33 -0.42 -0.45 -0.34 -0.27 -0.69 -0.58 -0.52Observation bore

65846_1 -0.32 -0.41 -0.44 -0.33 -0.26 -0.67 -0.56 -0.5065846_2 -0.35 -0.44 -0.47 -0.36 -0.28 -0.72 -0.61 -0.54

6.6.3 Kialla GMU

Observation bore 56424 was selected within the Kialla GMU to indicate the water level changes under the scenarios in both the Calivil Formation and Renmark Group aquifers. Modelled groundwater levels are reported for both aquifers at this location, even though this bore only screened within the Renmark Group. Average water levels under the various scenarios vary from 0.35 m higher to 2.08 m lower than under Scenario A (Table 6-12).


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Table 6-12. Median groundwater level in the Kialla GMU under Scenario A, and changes from this level under scenarios B, C and D

Median groundwater level changes A B Cdry Cmid Cwet Ddry Dmid Dwet m AHD change from Scenario A (m) Calivil Formation 92.55 -1.08 -1.46 -0.19 0.35 -2.09 -0.73 -0.14Renmark Group 92.53 -1.08 -1.46 -0.18 0.34 -2.08 -0.73 -0.14Average 92.54 -1.07 -1.46 -0.19 0.35 -2.08 -0.73 -0.14

The water balance is almost entirely composed of interactions with surrounding GMUs (Table 6-13). Groundwater extraction from the GMU is a very small proportion of total outflows. Lateral groundwater flows out of the GMU occur in response to pumping in deep lead aquifers that is occurring in areas to the north and west of Kialla GMU. This water is replenished by vertical leakage from overlying aquifers.

Table 6-13. Average annual water balance for the Kialla GMU under scenarios A, B, C and D



GL/y Inflows Total diffuse recharge 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Head dependent boundary 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0River recharge 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Leakage from overlying aquifer 9.3 16.4 16.4 16.5 16.3 16.3 16.5 16.3 16.3Lateral flow 6.2 6.6 6.6 6.6 6.6 6.6 6.6 6.6 6.5Total 15.5 23.0 23.0 23.1 22.9 22.9 23.1 22.9 22.8Outflows Groundwater pumping 0.0 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5Head dependent boundaries 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Leakage to overlying aquifer 1.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Lateral flow 14.5 22.5 22.5 22.7 22.5 22.5 22.7 22.4 22.3To rivers 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Total 15.6 23.0 23.0 23.2 23.0 23.0 23.2 22.9 22.8

The groundwater indicators for Kialla GMU are listed in Table 6-14. The results show that groundwater security is high under all scenarios. The environmental indicator is 0.02 under all scenarios reflecting that the groundwater balance of the GMU is dominated by throughflow rather than groundwater extraction. Groundwater drawdowns (drought indicator) range between 1.53 m under Scenario A and 3.40 m under Scenario Ddry.

Table 6-14. Groundwater indicators for the Kialla GMU under scenarios A, B, C and D


Security indicator percent 100% 100% 100% 100% 100% 100% 100% 100%Environmental indicator ratio 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02Drought indicator m Average -1.53 -2.49 -2.81 -1.71 -1.23 -3.40 -2.25 -1.67Observation bore

56424_3 -1.53 -2.49 -2.81 -1.71 -1.23 -3.40 -2.25 -1.6756424_4 -1.53 -2.49 -2.81 -1.71 -1.23 -3.40 -2.25 -1.67


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6.6.4 Nagambie GMU

Observation bores 46195 and 98178 were selected to indicate the water level changes under the scenarios in Calivil Formation aquifer within the Nagambie GMU. Table 6-15 shows the effect of the various scenarios on the mean groundwater water levels. Groundwater levels under the various climate change scenarios vary from 0.21 m higher to 2.09 m lower than under Scenario A.

Table 6-15. Median groundwater level in individual bores in the Nagambie GMU under Scenario A, and changes from this level under scenarios B, C and D

Median groundwater level changes A B Cdry Cmid Cwet Ddry Dmid Dwet m AHD change from Scenario A (m) 46195_3 107.93 -0.58 -0.77 -0.1 0.21 -1.1 -0.37 -0.0498178_3 118.43 -0.64 -0.84 -0.08 0.21 -3.08 -1.84 -1.43Average 113.18 -0.61 -0.81 -0.09 0.21 -2.09 -1.11 -0.74

The Nagambie GMU comprises the deep lead aquifers and its water balance is dominated by fluxes across the GMU boundaries (Table 6-16). There are also small volumes of direct rainfall recharge in the southern highlands where the Calivil formation outcrops around the basin margins.

The majority of recharge occurs as leakage from the overlying Shepparton GMU given the GMU lies near the southern boundary of the basin and is enclosed largely by outcropping bedrock. This in turn is likely to have a strong influence on surface water flows in the Goulburn River catchment.

Table 6-16. Average annual water balance for the Nagambie GMU under scenarios A, B, C and D



GL/y Inflows Total diffuse recharge 0.2 0.4 0.4 0.4 0.4 0.4 1.1 1.2 1.1Head dependent boundary 0.0 0.1 0.2 0.3 0.1 0.1 1.1 0.6 0.5River recharge 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Leakage from overlying aquifer 7.5 8.1 7.4 7.3 8.0 8.4 6.7 7.4 8.0Lateral flow 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Total 7.7 8.6 8.0 8.0 8.5 8.9 8.9 9.2 9.6Outflows Groundwater pumping 0.0 2.3 2.3 2.3 2.3 2.3 3.9 3.9 4.1Head dependent boundaries 1.5 0.7 0.4 0.4 0.7 0.8 0.1 0.2 0.3Leakage to overlying aquifer 5.1 3.8 3.4 3.3 3.7 4.0 2.7 3.1 3.3Lateral flow 1.2 1.8 1.9 1.9 1.9 1.8 2.1 1.9 1.8To rivers 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0Total 7.8 8.6 8.0 7.9 8.6 8.9 8.8 9.1 9.5

The groundwater indicators for the Nagambie GMU are listed in Table 6-17. The results show that groundwater security is high under all scenarios. The environmental indicator is 0.27 under Scenario A, and increases to 0.43 under Scenario Ddry. An increase in this value towards 1 represents a decrease of water for environmental purposes. The relatively low values of this indicator reflect the relatively low rate of groundwater pumping within this GMU. Groundwater drawdowns (drought indicator) range between 0.75 m for Scenario A and 2.65 m under Scenario Ddry.


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Table 6-17. Groundwater indicators for the Nagambie GMU under scenarios A, B, C and D

Groundwater indicators A B Cdry Cmid Cwet Ddry Dmid DwetSecurity indicator percent 100% 100% 100% 100% 100% 100% 100% 100%Environmental indicator ratio 0.27 0.28 0.29 0.27 0.26 0.43 0.42 0.42Drought indicator m Average -0.75 -1.18 -1.31 -0.81 -0.58 -2.65 -1.93 -1.64Observation bore

46195_3 -0.90 -1.27 -1.39 -0.96 -0.75 -1.76 -1.29 -1.0798178_3 -0.71 -1.22 -1.38 -0.77 -0.53 -3.71 -2.77 -2.43

6.7 Water balances for groundwater management units not modelled and unincorporated areas

Alexandra GMU and Kingslake GMU are not covered by the Southern Riverine Plains groundwater model. They were analysed using a simple water balance approach because these two GMUs supply a relatively small proportion of the groundwater extracted in the region. A water balance assessment was also done for the unincorporated areas with fair groundwater quality (< 1,500 mg/L TDS) in the upper part of the catchment that have the potential for development in the future. These unincorporated areas are mostly upstream of Seymour in the Goulburn Basin and upstream of Goorambat in the Broken Basin. The coverage of this water balance assessment is approximately 11, 000 km2.

6.7.1 Groundwater extraction

Table 6-18 summarises current (2004/05) groundwater usage within the southern parts of the region. Estimates were made for groundwater use from unmetered bores, including a nominal usage of 2 ML/year for stock and domestic bores. Total 2004/05 groundwater use for the region is estimated at 5.65 GL/year.

Table 6-18 also includes estimates of future (2030) groundwater extraction volumes. Urban use and stock and domestic use were assumed not to increase above current levels. All other use (principally for irrigation) is assumed to increase by 3.65 percent per year until it reaches the current entitlement volume. This rate is equal to the mean annual increase in water usage across Australia between 1983/84 and 1996/97 (Land & Water, 2000). Other use in 2030 is assumed to equal the current entitlement volume for the low priority GMUs and unincorporated areas of the region. Total groundwater use in the year 2030 is estimated to be 11.49 GL/year. Total future extraction can exceed total entitlement since entitlements do not include stock and domestic bores.

Table 6-18. Estimated groundwater extraction for the southern parts of the Goulburn-Broken region

Code Name Licenced extraction (2004/05)

Stock and domestic (2004/05)

Total current extraction (2004/05)

Total entitlement**

Future extraction**(2030)

GL/y V11 Alexandra GMU 0.6 0.104 0.704 1.714 1.520V12 Kinglake GMU* 0.510 0.534 1.044 1.490 1.738– Unincorporated Areas 3.540 0.362 3.902 7.866 8.228 Total 4.650 1.000 5.650 11.070 11.486* Approximately 78 percent of the Kinglake GMU falls within the Goulburn Basin, with the remainder falling outside the Murray-Darling Basin. Groundwater entitlements and use are for the portion of the GMU that falls within the region only. ** Entitlements do not include bores for stock and domestic use. Future extraction values do include stock and domestic use.


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6.7.2 Estimates of rainfall recharge and environmental indicator

Rainfall recharge is the largest factor within the water balance and is the focus of this assessment.

Estimates of rainfall recharge are available for both Kinglake and Alexandra GMUs. Recharge to the fractured rock aquifer of the Kinglake GMU was estimated at 5 percent of annual rainfall, or 5.70 GL/year (Reid, 2004). The recharge rate to the portion of the GMU within the MDB (78 percent) is assumed to be 4.45 GL/year. Recharge to the unconfined Quaternary aquifer was estimated for the Alexandra GMU at 10 percent of annual rainfall, or 1.89 GL/year (Reid, 2004).

Recharge to unincorporated areas of the upper region was estimated by considering land cover and geology. Approximately 60 percent of the region is covered by forest, and rainfall recharge to these areas was assumed to be 1 percent of annual rainfall. Rainfall recharge of 5 percent of annual rainfall has been used for cleared Palaeozoic bedrock areas (approximately 10 percent of the region), consistent with that used for the Kinglake GMU. A rainfall recharge of 10 percent of rainfall (consistent with that used for the Alexandra GMU) was used for Quaternary alluvium (approximately 20 percent of the catchment), and 4 percent of rainfall has been used for granite areas in the southern part of the basin (10 percent of the catchment area). Total recharge to the region is thus estimated at 245 GL/year, including 238 GL/year to the unincorporated area and 6.34 GL/year to the GMUs.

The environmental indicator (ratio of extraction to recharge) indicates the potential level of stress within an aquifer. The ratio of current (2004/05) groundwater extraction to recharge for the entire area is 0.023 (Scenario A).

The impact of each scenario on total annual recharge and on the ratio of extraction to recharge has been determined via RSFs that are applied to the Scenario A volume of recharge to the system (Table 6-19, Table 6-20). Scenario B results in an increase of 0.013 in the ratio of extraction to recharge due to a decline in the annual recharge volume. Scenario Cmid and Cdry lead to an increase in the ratio of extraction to recharge by 0.002 and 0.007 respectively. Scenario Cwet differs from all other scenarios, in that it results in a 0.001 decrease in the ratio of extraction to recharge, due to higher rainfall in the 2030 climate change predictions. Scenario D incorporates both reduced recharge and increased groundwater extraction. Scenarios Dwet, Dmid and Ddry lead to increases in the ratio of extraction to recharge by 0.021, 0.027 and 0.037 respectively.

The impact of Scenario A groundwater extraction on recharge was also assessed in terms of individual GMUs and the unincorporated area. The ratio of extraction to groundwater recharge will be more variable for individual GMUs than on a region-wide scale as groundwater development is predominantly concentrated in GMUs and WSPAs. The ratio of extraction to recharge in the Kinglake GMU is currently 0.23, but increases to 0.50 under Scenario Ddry. The extraction to recharge ratio in the Alexandra GMU increases from 0.37 under Scenario A to 1.03 under Scenario Ddry.

Table 6-19. Recharge in low priority groundwater management units under scenarios A, B, C and D

A B Cdry Cmid Cwet Ddry Dmid Dwet GL/y Alexandra GMU 1.9 1.2 1.5 1.8 2.0 1.5 1.8 2.0Kinglake GMU 4.4 2.8 3.5 4.2 4.7 3.5 4.2 4.7Unincorporated Areas 239 153 186 224 253 186 224 253Total 245 157 191 230 260 191 230 260Percent change - -36% -22% -6% +6% -22% -6% +6%


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Table 6-20. Environmental indicator (ratio of extraction to recharge) groundwater management units not modelled, and unincorporated areas under scenarios A, B, C and D

A B Cdry Cmid Cwet Ddry Dmid Dwet ratio Alexandra GMU 0.37 0.58 0.48 0.40 0.35 1.03 0.86 0.76Kinglake GMU 0.23 0.37 0.30 0.25 0.22 0.50 0.42 0.37Unincorporated Areas 0.02 0.03 0.02 0.02 0.02 0.04 0.04 0.03Total 0.02 0.04 0.03 0.03 0.02 0.05 0.05 0.04Note: Groundwater extraction includes both licensed extraction and stock and domestic use

6.7.3 Impact of extraction on streamflow

Groundwater pumping often causes a decline in the groundwater levels surrounding a bore. In the case of a gaining river, the rate of groundwater discharge to the river decreases and reduces the volume of stream flow. In the case of a losing river, a decline in groundwater level will increase leakage from the river into the underlying aquifer and will again decrease flow in the river.

Scenarios A, B and C each assume that groundwater extraction is equal to the current extraction volume of 5.65 GL/year and under Scenario D conditions groundwater extraction volumes are estimated at 11.5 GL/year. A moderate to high level of connectivity exists in the highland area of the region and so the 5.8 GL/year increase in extraction under Scenario D is considered to directly impact streamflow. (It has been assumed current development has already impacted the river.) This may slightly overestimate the actual impact but it is considered to be a reasonable assumption in the absence of other information. The impact of this extraction will be most significant during periods of low streamflow.

The flow rate of the Goulburn River at Seymour during low flow conditions is approximately 50 GL over a 3 month period and it is approximately 2.3 GL for the Broken River at Goorambat. The increase in extraction under Scenario D is approximately 5.0 GL/year in the Goulburn catchment and 0.9 ML/year in the Broken catchment. If the time delay between groundwater pumping and impact on the river is very small (due to proximity of most bores to the river), then the river loss over the three month low flow period will be one-quarter of these volumes. This is approximately 1.2 and 0.2 GL/year for the Goulburn and the Broken low priority areas, respectively. Increased groundwater pumping under Scenario D has the potential to reduce low flows in the Goulburn and Broken Rivers by 2.5 and 9 percent, respectively. There will be significant time lags before these streamflow reductions are realised if the distance of the bores from the river is greater.

6.8 Conjunctive water use indicator

Groundwater can provide a secure water source during drier periods. Irrigators may elect to change from surface water to groundwater during years of low flow where such exchanges are feasible. Even without this, the lower surface water diversions in low flow years mean that groundwater forms a higher proportion of total diversions in those years. Table 6-21 shows these ratios for years of lowest surface water diversions up to a year with average flow.

Groundwater forms 10 to 16 percent of total diversions in the region under current conditions. This rises to 11 to 29 percent under Scenario Cmid, 15 to 63 percent under Scenario Cdry and 11 to 19 percent under Scenario Cwet. Groundwater use rises to 17 to 41 percent under Scenario Dmid, 23 to 72 percent under Scenario Ddry and 16 to 29 percent under Scenario Dwet.

Groundwater forms a minor source of water for the region as a whole under average flow years but is important in drier years. Its significance increases under the drier future conditions and it becomes a major source of water for low flow years in general.


6 Groundw

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Table 6-21. Conjunctive water use indicator: ratio of groundwater to total water diversion in the Goulburn-Broken region on average and in 1-, 3- and 5-year periods of lowest surface water diversions under scenarios A, B, C and D

A B Cdry Cmid Cwet Ddry Dmid DwetLowest 1-year period 16% 53% 63% 29% 19% 72% 41% 29%Lowest 3-year period 13% 24% 28% 16% 14% 39% 24% 21%Lowest 5-year period 13% 22% 25% 15% 13% 36% 23% 21%Average 10% 14% 15% 11% 11% 23% 17% 16%


Groundwater provides 10 percent of the total water diverted with this increasing to 16 percent in drier years. This percentage is likely to increase under future scenarios of possibly up to 70 percent under the driest scenario. Most of the groundwater extraction occurs from a regional aquifer that extends across the region and into NSW and neighbouring regions. The groundwater balance of smaller GMUs is dominated by the extraction from neighbouring GMUs. Lateral flows from neighbouring areas account for 15 percent of the groundwater budget. The Shepparton area differs from other areas in that significant pumping occurs from Shepparton Formation mainly for the purpose of lowering watertables. Much of the extraction induces a reduction in groundwater evapotranspiration. Some of the extraction causes a reduction in river flow. The total impact of current extraction on the stream is estimated to be 20 GL/year (14.6 GL/year from modelled area and 5.6 GL/year from non-modelled areas). The total impact on the streams under Scenario Dmid is estimated to be 37 GL/year (25.8 GL/year from modelled areas and 11.5 GL/year from non-modelled areas). Some, but not all of these impacts have been included in the river modelling (Chapter 4). Reasons for not including impacts are: (i) some impacts occur on Broken Creek, which is not represented in the REALM model, and (ii) some impacts less than 2 GL/year have been ignored, since they are within the uncertainty of the analysis.

6.10 References

Braaten R and Gates G (2002) Groundwater – surface water interaction in inland New South Wales: a scoping study. Water Science

and Technology. 48(7): 215–224. Goulburn Broken CMA (2002) Goulburn-Broken Dryland Salinity Management Plan 1995-2001 Review. Second generation salinity plan.

Goulburn Broken Catchment Management Authority. Kevin P (1992) Groundwater and Salinity Processes in the Uplands of the Loddon Catchment. Centre for Land Protection Research,

Bendigo, May 1992. Reid M (2004) Audit of Permissible Annual Volumes for 35 Victorian Groundwater Management Areas. Departments of Primary

Industries. SKM (1998a) Permissible Annual Volume Project –The Alexandra GMA. Report prepared for the Department of Natural Resources and

Environment, Victoria. Sinclair Knight Merz. SKM (1998b) Permissible Annual Volume Project –The Kinglake GMA. Report prepared for the Department of Natural Resources and

Environment, Victoria. Sinclair Knight Merz. SKM (2006) Draft Conceptual Model. Report prepared for Goulburn-Murray Water. Sinclair Knight Merz. SKM (2007) Groundwater – Surface Water Connectivity in the Goulburn-Broken Catchment. report prepared for the Murray Darling

Basin Commission. Sinclair Knight Merz.


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7 Environment This chapter presents the environmental assessments undertaken for the Goulburn-Broken region. It has four sections:

• a summary • an overview of the approach • a presentation of results • a discussion of key findings.

7.1 Summary


• Assessment of the environmental implications of changes in water availability is largely beyond the terms of reference of this project (Chapter 1). The exception is reporting against environmental water allocations and quantified environmental flow rules specified in water sharing plans. Otherwise, environmental assessments form a very small part of the project.

• The Goulburn-Broken is a highly regulated system with large volumes of water extracted and transferred to other regions. Environmental flows are provided via environmental water reserves which include ‘passing flow’ requirements.

• Changes in low flows that maintain connectivity of fish habitat and in high flows that are important to ecological and geomorphic processes on the lower Goulburn River are assessed.

7.1.2 Key messages

• Water resources development has increased more than four-fold the average period between large (1000 GL/month) beneficial floods to the lower Goulburn River floodplain. Additionally, undesirably low flows that diminish deep water pools and degrade native fish habitat are now more prevalent – occurring about twice a year on average rather than once every 7.6 years.

• A continuation of the recent climate (1997 to 2006) would mean that large flood events for the lower Goulburn Region floodplain would cease with serious ecological consequences. This climate would also increase the occurrence of undesirably low flows, which would further degrade the habitat value of the deep pools on the lower river, with likely consequences for endangered fish species.

• The best estimate 2030 climate would see substantial reductions in the occurrence and volumes of high flows to the lower Goulburn River floodplain. The occurrence of undesirably low flows would increase slightly.

• The dry 2030 climate extreme would lead to similar hydrological changes and ecological consequences as a continuation of the recent climate.

• The wet 2030 climate extreme would not lead to much change from current conditions for flooding of the lower Goulburn River floodplain. However, the occurrence of undesirably low flows would increase slightly compared to current conditions.

• Additional catchment development (farm dams and groundwater extraction) would have minimal impact over and above the impacts of climate change described above.

7.1.3 Uncertainty

The main uncertainties in the analysis and reporting include:

• Aquatic and wetland ecosystems are highly complex and many factors in addition to water regime can affect ecological features and processes, such as water quality and land use practices.


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• The indicators are based on limited hydrology parameters with no direct quantitative relationships for environmental responses. This study only makes general observations on the potential implications of changed water regimes and some related ecological responses.

• Considering a few of the important environmental assets and using a limited number of indicators to represent overall aquatic ecosystem outcomes is a major simplification. Actual effects on these and other assets or localities are likely to vary.

• Uncertainties expressed in Chapters 3, 4 and 5 affect the hydrologic information used in the environmental assessments.

7.2 Approach

This chapter focuses on the specific rules that apply to the provision of environmental water in the Goulburn-Broken region and on the assessment of hydrological indicators defined by prior studies for key environmental assets in the region. A broader description of the catchment, water resources and important environmental assets in provided in Chapter 2.

7.2.1 Summary of environmental flow rules

The Goulburn and Broken Environmental Water Reserve (DSE, 2007) has the following components: (i) passing flows released as a condition of consumptive bulk entitlements held by North East Water and Goulburn Murray Water; and (ii) all other water in the catchment not allocated for consumptive use – that is, ‘above cap’ water.

There are many environmental flow rules and passing flow requirements in the Goulburn-Broken region, in both regulated and unregulated systems. Some of the passing flow requirements in unregulated systems are presented below for the Delatite and Yea rivers.

For the Delatite River, the Bulk Entitlement (Mansfield) Conversion Order 1995 requires:

• a minimum passing flow of 18 ML/day • when flow is less than 18 ML/day, the authority must pass the entire flow • when flow is between 18 and 20.2 ML/day, the authority must pass 18 ML/day • when flow is between 20.2 and 30 ML/day, the authority must pass the entire flow less 2.2 ML/day • when flow is between 30 and 32.2 ML/day, the authority must pass 27.8 ML/day • when flow is greater than 32.2 ML/day, the authority must pass the entire flow less 4.4 ML/day.

For the Yea River, the Bulk Entitlement (Yea) Conversion Order 1997 requires:

• a minimum passing flow of 3.6 ML/day • when flow is less than 7.2 ML/day, the authority must pass half the flow • when flow is greater than 7.2 ML/day, the authority must pass the entire flow less 3.6 ML/day.

7.2.2 Environmental assets and indicators

The environmental assets (Figure 7-2) and hydrological indicators (Table 7-1) selected for use in the Goulburn-Broken region are described below. The description of the lower Goulburn River floodplain is from Environment Australia (2001), unless cited otherwise.


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Figure 7-1. Location map of environmental assets

Lower Goulburn River floodplain

Parts of the lower Goulburn River floodplain are listed in Environment Australia (2001) as a nationally important wetland (VIC052) with the nominated area covering some 13,000 ha downstream of Goulburn Weir to the Murray River junction.

The wetland consists of a large number of billabongs, anabranches and marginal swamps and includes Gemmills Swamp, Reedy Swamp State Wildlife Refuges and Loch Gary Wildlife Management Cooperative Area. The floodplain receives water from the river via diversions from Goulburn Weir and via a number of effluent channels.

The wetland vegetation is dominated by River Red Gum (Eucalyptus camaldulensis) forest and woodland and more limited areas of Grey Box (E. mircocarpa) and Yellow Box (E. melliodora), White Box (E. albens) and Black Box (E. largiflorens). Other flora includes a range of threatened species. A large number of faunal species are recorded, including 34 waterbird species recorded in Gemmills Swamp. Over 1000 Ibis are recorded regularly at Reedy Swamp. Threatened species that are recorded include Magpie Geese (Anseranas semipalmata), Bush Thick-knee (Burhinus magnirostris) and Superb Parrot (Polytelis swainsoni). The floodplain is used extensively for recreation due to the public land areas. Land tenure is mostly State Forest but also the Wildlife Refuges and Management areas listed above.

Cottingham et al. (2003a) identified the flow levels in the lower Goulburn River at which flooding of the wetlands begins. This flow is 55 GL/day at McCoys Bridge (Loch Garry). The primary flooding period is June to November inclusive (DSE, pers. comm.). Due to the monthly time step of the REALM river model used for this region (Chapter 4) the 55 GL/day flow was converted to an equivalent flow of 1000 GL/month. To establish this equivalent monthly flow, the data used by Cottingham et al. (2003a) were converted to monthly totals, and then the monthly threshold which gave an equivalent number of events (and identified the correct ‘event’ months) was determined.

Lower Goulburn River

Based on advice from the Victorian Department of Sustainability and Environment (DSE) ’Reach 5’ from Cottingham et al. (2003b) on the lower Goulburn River was also selected for assessment. This reach extends from Loch Garry to the confluence with the Murray River, and as indicated above this reach is a wetland of national importance.

Reach 5 has a range of environmental values (Cottingham et al., 2003b) including providing habitat for 11 species of native fish: Silver Perch (Bidyanus bidyanus), River Blackfish (Gadopsis marmoratus), Flat-headed Galaxias (Galaxias rostratus), Western Carp Gudgeon (Hypseleotris klunzingeri), Trout Cod (Maccullochella macquariensis), Murray Cod (Maccullochella peelii peelii), Golden Perch (Macquaria ambigua), Murray Rainbowfish (Melanotanenia fluviatilis), Flat-headed Gudgeon (Philypnodon grandiceps), Australian Smelt (Retropinna semoni) and Freshwater catfish (Tandanus tandanus). Introduced species such as Carp (Cyprinus carpio) are also found in the area.


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Based on DSE advice, the low flows which protect in-channel habitat in this reach were assessed. Cottingham et al. (2003a) recommends a minimum flow of 610 ML/day to sustain deep water habitat for large bodied fish. Again, due to the monthly time step of the REALM river model used for this region (Chapter 4), the 610 ML/day flow was converted to an equivalent flow of 18.3 GL/month. The conversion was made simply by multiplying the daily value by 30 days/month. The assessments report the length (average and maximum) of the periods for which flow does not fall below this target flow level at Goulburn Weir.

Figure 7-2. Satellite image of the lower Goulburn River and floodplain

Table 7-1. Definition of environmental indicators

Goulburn River indicators Description

Lower Goulburn River floodplain Average period between flooding Average period (years) between flows exceeding 1000 GL/month during June to November at

McCoys Bridge gauge Maximum period between flooding Maximum period (years) between flows exceeding 1000 GL/month during June to November at

McCoys Bridge gauge Average flooding volume per event Average flow volume per event above 1000 GL/month during June to November at McCoys

Bridge gauge Average flooding volume per year Average flow volume per year above 1000 GL/month during June to November at McCoys Bridge

gauge Lower Goulburn River

Average period between undesirably low flows

Average period (years) for which flow is continuously above 18.3 GL/month at Goulburn Weir

Maximum period between undesirably low flows

Maximum period (years) for which flow is continuously above 18.3 GL/month at Goulburn Weir


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7.3 Results

The projected changes in the hydrological indicators are listed for the each scenario in Table 7-2 based on the outputs from the REALM river model used for the Goulburn-Broken region.

Table 7-2. Environmental indicator values under scenarios P and A, and percentage change (from Scenario A) in indicator values under scenarios B, C and D. In the drier scenarios there are no events (n.e.) and hence the volume indicators cannot be calculated and the

percentage change in period indicators are not meaningful. Negative percentage changes indicate reductions.

P A B Cdry Cmid Cwet Ddry Dmid Dwet years percent change from A Lower Goulburn River floodplain

Average period between flooding 2.5 10.7 n.e. n.e. 82% 0% n.e. 82% 0%Maximum period between flooding 11 37 n.e. n.e. 4% 0% n.e. 4% 0%

GL Average flooding volume per event 2056 2950 n.e. n.e. -32% -17% n.e. -32% -17%Average flooding volume per year 722 239 n.e. n.e. -62% -17% n.e. -62% -17%

Lower Goulburn River years Average period between undesirably low flows 7.6 0.47 -36% -39% -13% -3% -39% -13% -2%Maximum period between undesirably low flows 37.7 1.67 -40% -20% -20% -15% -20% -20% -15%


Lower Goulburn River floodplain

Under without-development conditions (Scenario P), the 1000 GL/month flows that inundate the lower floodplain of the Goulburn River were relatively common – occurring every 2.5 years on average and never more than about a decade between events. However, water resource development has had a major impact on the frequency of these events. There is now an average of 11 years between flooding events, and the maximum period between events is 37 years. Although the average volume of individual flooding events has increased by 43 percent, the reduction in the number of events means that the average annual flooding volume is only one-third of the without-development annual flooding volume. This assessment is consistent with Cottingham et al. (2003b) who report that 55 GL/day flows in the lower river occurred on about 3 percent of days under without-development conditions, but now occur on less than 1 percent of days.

A long-term continuation of the 1997 to 2006 climate (Scenario B) would mean a cessation of significant flooding of the lower floodplain which would have major impacts on floodplain ecology.

Under the best estimate 2030 climate the changes would be much smaller than under a long-term continuation of the recent climate. However, there would be a 82 percent increase (about 8 years) in the average period between high flow events and a 4 percent increase (about 1.5 years) in the maximum period between events, compared with Scenario A. The average flooding volume of these events would be reduced by 32 percent, meaning that the average annual flooding volume of floods would be reduced by 62 percent. It is likely these changes would have substantial ecological consequences.

Scenario Cdry would lead to a cessation of significant flooding of the lower floodplain and would have major impacts on floodplain ecology. Under Scenario Cwet, high flows frequencies would be very similar to current conditions; however, the volumes of these events would reduce by 17 percent.

The small projected increases in farm dams and groundwater development by 2030 under Scenario D would have almost no additional impact on the frequencies and volumes of 1000 GL/month flow events to those resulting from climate change.


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Lower Goulburn River

Water resource development has greatly impacted the frequency with which flows fall below the target minimum flow level in the lower Goulburn River, with the average period between occurrences of undesirably low flows reducing from 7.6 years to less than 6 months.

The maximum period between undesirably low flows was more than 37 years under without-development conditions, but is now less than 2 years. This trend is similar to information provided in Cottingham et al. (2003a) that shows that flows in this river reach almost always exceeded around 600 ML/day under without-development conditions, but that flows now drop to this level or below on about 75 percent of days. These changes are likely to have serious consequences for the flora and fauna resident in the deep pools and habitat for native fish, some of which are endangered.

A long-term continuation of the 1997 to 2006 climate (Scenario B) would lead to a further 36 percent reduction in the average period between undesirably low flows, with the maximum period between reducing by 40 percent from current conditions. This is in addition to the changes from without development to current conditions. Considering the changes from without development to Scenario B the average period between undesirably low flows would reduce from once every 7.6 years to three to four times per year. These changes are likely to have further consequences for the flora and fauna resident in the deep pools of the lower river.

Under Scenario Cmid there would be a smaller decrease in the average and maximum periods between undesirably low flows compared to current conditions. Scenario Cdry would lead to conditions similar to those under a continuation of the 1997 to 2006 climate, with a 39 percent reduction in the average period between undesirably low flows and a 20 percent reduction in the maximum period between undesirably low flows, with similar consequences for the ecological conditions of the deep pools. Under Scenario Cwet, both the average and maximum periods between undesirably low flows would be reduced only slightly from current conditions.

The small projected increases in farm dams and groundwater development under Scenario D would have almost no additional impacts to those discussed above due to climate change.

7.5 References

Cottingham P, Stewardson M, Crook D, Hillman T, Roberts J and Rutherford I (2003a) Environmental flow recommendations for the Goulburn River below Lake Eildon. CRC for Freshwater Ecology and CRC for Catchment Hydrology, Technical Report 01/2003.

Cottingham P, Crook D, Hillman T, Roberts J, Rutherford I and Stewardson M (2003b) Flow-related environmental issues associated with the Gouburn River below Lake Eildon. A report to the Department of Sustainability and Environment, Victoria and the Murray-Darling Basin Commission. CRC for Freshwater Ecology and CRC for Catchment Hydrology..

DSE (2007) State Water Report 2005/06 – a statement of Victorian Water Resources. Department of Sustainability and Environment, Victoria, East Melbourne.

Environment Australia (2001) A Directory of Important Wetlands in Australia. Third Edition. Environment Australia, Canberra. Available at: http://www.environment.gov.au/water/publications/environmental/wetlands/pubs/directory.pdf


Appendix A

Rainfall-runoff results for all subcatchm

ents

Appendix A Rainfall-runoff results for all

subcatchments

Table A-1. Summary of modelling results for all subcatchments under scenarios A and C

Scenario A Scenario Cdry Scenario Cmid Scenario Cwet

Modelling catchment

Area Rainfall APET Runoff Runoff coefficient

Runoff contribution

Rainfall Runoff Rainfall Runoff Rainfall Runoff

km2 mm percent percent change from Scenario A

4042041 737 542 1273 38 7% 1% -17% -43% -4% -13% 2% 2%

4042061 81 874 1216 162 19% 0% -19% -42% -4% -12% 0% -2%

4042082 195 932 1204 198 21% 1% -19% -41% -4% -12% 0% -2%

4042103 742 458 1275 20 4% 0% -17% -44% -4% -15% 2% 3%

4042104 342 493 1297 27 5% 0% -15% -37% -3% -12% 4% 9%

4042122 569 951 1198 172 18% 3% -19% -48% -4% -15% 0% -3%

4042141 742 484 1283 26 5% 1% -16% -40% -4% -13% 2% 4%

4042161 248 778 1240 87 11% 1% -19% -48% -4% -15% 0% -2%

4042163 88 629 1260 58 9% 0% -19% -47% -4% -14% 0% -2%

4042181 417 943 1172 160 17% 2% -19% -51% -4% -16% 0% -3%

4042190 336 672 1245 75 11% 1% -19% -47% -4% -15% 0% -2%

4042243 188 807 1221 140 17% 1% -19% -42% -4% -12% 0% -2%

4052013 629 821 1151 103 13% 2% -19% -49% -4% -16% 0% -4%

4052014 1727 887 1154 194 22% 10% -19% -44% -4% -14% 0% -3%

4052015 1088 1274 1118 426 33% 14% -19% -38% -4% -11% 0% -3%

4052042 369 516 1244 28 5% 0% -19% -47% -4% -15% 0% -2%

4052043 208 499 1243 32 6% 0% -19% -48% -4% -15% 0% -2%

4052321 939 491 1265 26 5% 1% -18% -48% -4% -15% 0% -1%

4052580 3911 1183 1108 377 32% 44% -19% -43% -4% -13% 0% -3%

4052593 1299 569 1209 67 12% 3% -19% -54% -4% -17% -1% -2%

4052594 1495 691 1158 97 14% 4% -19% -54% -4% -18% -1% -3%

4052595 481 743 1174 136 18% 2% -19% -46% -4% -14% 0% -2%

4052692 2626 663 1225 83 12% 7% -19% -49% -4% -16% 0% -2%

4067041 2882 448 1259 23 5% 2% -17% -45% -4% -14% 1% 0%

22337 764 1197 149 20% 100% -19% -44% -4% -13% 0% -2%


App

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Table A-2. Summary of modelling results for all subcatchments under scenarios A and D

Modelling catchment

A runoff Plantations increase

Farm dam increase Ddry runoff Dmid runoff Dwet runoff

mm ha ML ML/km2 percent change from Scenario A

4042041 38 0 531 0.7 -45% -16% 0%

4042061 162 0 26 0.3 -42% -13% -2%

4042082 198 0 53 0.3 -41% -12% -2%

4042103 20 0 99 0.1 -45% -15% 2%

4042104 27 0 353 1.0 -41% -17% 3%

4042122 172 0 158 0.3 -48% -15% -3%

4042141 26 0 434 0.6 -43% -16% 1%

4042161 87 0 65 0.3 -48% -15% -3%

4042163 58 0 22 0.3 -47% -15% -3%

4042181 160 0 159 0.4 -51% -16% -4%

4042190 75 0 87 0.3 -47% -15% -3%

4042243 140 0 52 0.3 -42% -12% -2%

4052013 103 0 803 1.3 -51% -17% -6%

4052014 194 0 1005 0.6 -44% -14% -3%

4052015 426 0 83 0.1 -38% -11% -3%

4052042 28 0 33 0.1 -48% -15% -2%

4052043 32 0 3 0.0 -48% -15% -2%

4052321 26 0 80 0.1 -49% -16% -1%

4052580 377 0 1242 0.3 -43% -13% -3%

4052593 67 0 392 0.3 -54% -18% -3%

4052594 97 0 1871 1.3 -56% -20% -5%

4052595 136 0 216 0.4 -46% -15% -3%

4052692 83 0 811 0.3 -49% -16% -3%

4067041 23 0 161 0.1 -45% -15% 0%

149 0 8737 0.4 -44% -14% -3%


Appendix B

River m

odelling reach mass balances

Appendix B River modelling reach mass balances

Reach 1 - Tributaries into Lake Eildon

A B Cwet Cmid Cdry Dwet Dmid Ddry

Model start date Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895 Jul-1895

Model end date Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006 Jun-2006

GL/y percent change from Scenario A

Storage volume

Change over period -13.7 25% 12% 23% 25% 12% 23% 25%

Inflows

Subcatchments

Directly gauged 0.0 0% 0% 0% 0% 0% 0% 0%

Indirectly gauged 1475.6 -36% -3% -13% -43% -3% -13% -43%

Transfers from other Goulburn-Broken subcatchments

0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 1475.6 -36% -3% -13% -43% -3% -13% -43%

River groundwater gains 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 1475.6 -36% -3% -13% -43% -3% -13% -43%

Diversions

Water use

Licensed private diverters 0.0 0% 0% 0% 0% 0% 0% 0%

Irrigation districts 0.0 0% 0% 0% 0% 0% 0% 0%

Stock and domestic 0.0 0% 0% 0% 0% 0% 0% 0%

Urban supply 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 0.0 0% 0% 0% 0% 0% 0% 0%

Channel / pipe loss 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 0.0 0% 0% 0% 0% 0% 0% 0%

Outflows

End-of-system outflow

To d/s Goulburn (Reach 2) 1486.5 -36% -3% -13% -43% -3% -13% -43%

River groundwater loss 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 1486.5 -36% -3% -13% -43% -3% -13% -43%

Net evaporation* 2.8 131% 163% 149% 363% 163% 149% 361%

Sub-total 1489.3 -36% -2% -12% -42% -3% -12% -42%

Unattributed fluxes

River unattributed loss 0.0 0% 0% 0% 0% 0% 0% 0%



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Reach 2 - Goulburn River downstream of Lake Eildon to downstream Goulburn Weir (including East

Goulburn Main channel)





Storage volume

Change over period 0.0 0% 0% 0% 0% 0% 0% 0%

Inflows

Subcatchments

Directly gauged 0.0 0% 0% 0% 0% 0% 0% 0%


From u/s Goulburn (Reach 1) 1486.5 -36% -3% -13% -43% -3% -13% -43%

Sub-total 2866.8 -38% -3% -13% -44% -3% -13% -44%


Sub-total 2866.8 -38% -3% -13% -44% -3% -13% -44%

Diversions

Water use

Licensed private diverters 12.2 -9% 7% 3% 2% 7% 3% 2%

Irrigation districts 4.6 -27% -1% -6% -34% -1% -6% -34%

Stock and domestic 263.3 4% -1% 1% 3% -1% 1% 3%

Urban supply 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 263.3 -26% 0% -6% -31% 0% -6% -32%

Channel / pipe loss 95.4 -30% -1% -7% -36% -1% -7% -37%

Sub-total 358.6 -27% 0% -6% -33% -1% -6% -33%

Outflows


To Waranga Western Channel (to Reach 4)

1232.8 -24% -1% -5% -28% -1% -5% -28%



Sub-total 2344.6 -40% -3% -14% -46% -4% -15% -46%

Net evaporation* 8.6 -7% 9% 7% 22% 9% 7% 22%

Sub-total 2353.2 -40% -3% -14% -46% -4% -15% -46%

Unattributed fluxes

River unattributed loss 155.0 -34% -2% -11% -40% -2% -11% -40%



Appendix B

River m


Reach 3 – Waranga Western Channel from Waranga basin to downstream Greens Lake offtake





Storage volume

Change over period 0.3 -328% -78% -344% -328% -81% -344% -332%

Inflows

Subcatchments

Directly gauged 0.0 0% 0% 0% 0% 0% 0% 0%


Transfers from Goulburn Weir 1232.8 -24% -1% -5% -28% -1% -5% -28%

Sub-total 1237.3 -24% -1% -5% -28% -1% -6% -29%


Sub-total 1237.3 -24% -1% -5% -28% -1% -6% -29%

Diversions

Water use

Licensed private diverters 0.0 0% 0% 0% 0% 0% 0% 0%

Irrigation districts 469.5 -31% -2% -8% -38% -2% -8% -38%


Urban supply 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 469.5 -31% -2% -8% -38% -2% -8% -38%

Channel / pipe loss 212.9 -8% -1% -3% -8% -1% -3% -8%

Sub-total 682.4 -24% -1% -6% -28% -2% -6% -29%

Outflows


To d/s Waranga Western Channel (Campaspe Reach 5)

506.9 -25% 0% -5% -32% 0% -5% -32%


Sub-total 506.9 -25% 0% -5% -32% 0% -5% -32%

Net evaporation* 44.4 -12% 8% 5% 14% 8% 5% 14%

Sub-total 551.2 -24% 0% -4% -28% 0% -4% -28%

Unattributed fluxes

River unattributed loss 3.4 -3% 0% -1% -2% 0% -1% -2%



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Reach 4 - Goulburn River from downstream Goulburn Weir to downstream Shepparton





Storage volume


Inflows

Subcatchments

Directly gauged 257.2 -52% -2% -16% -49% -3% -16% -49%


Transfers from Broken River (Reach 8)

215.6 -58% -4% -17% -55% -4% -18% -55%


Sub-total 1588.1 -57% -5% -22% -61% -6% -23% -62%

River groundwater gains* 0.0 13% 1% 4% 14% 0% 2% -30%

Sub-total 1588.1 -57% -5% -22% -61% -6% -23% -62%

Diversions

Water use

Licensed private diverters 3.1 -20% 3% -2% -25% 3% -2% -25%



Urban supply 14.4 0% 0% 0% 0% 0% 0% 0%

Sub-total 17.5 -4% 1% 0% -5% 1% 0% -5%


Sub-total 17.5 -4% 1% 0% -5% 1% 0% -5%

Outflows



River groundwater loss** 0.0 -70% -12% -28% -77% -6% -22% -72%

Sub-total 1570.6 -58% -5% -22% -62% -6% -23% -62%

Net evaporation*** 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 1570.6 -58% -5% -22% -62% -6% -23% -62%

Unattributed fluxes


* Values in the row are those that were used in the river modelling. The correct value for Scenario A, to be consistent with the groundwater modelling, is 0.3 GL/year. The percentage change values for other scenarios are correct.

** Values in the row are those that were used in the river modelling. The correct value for Scenario A, to be consistent with the groundwater modelling, is 0.5 GL/year. The percentage change values for other scenarios are correct.

*** Evaporation from private licensed storages (GL/year) is not included as it is already accounted in diversions


Appendix B

River m


Reach 5 - Goulburn River from downstream Shepparton to downstream McCoy's Bridge





Storage volume


Inflows

Subcatchments

Directly gauged 0.0 0% 0% 0% 0% 0% 0% 0%



Irrigation drainage returns 28.4 -43% -4% -15% -46% -4% -15% -47%

Sub-total 1605.1 -58% -5% -22% -61% -6% -23% -62%

River groundwater gains* 0.2 -6% 3% 1% -8% -2% -7% -24%

Sub-total 1605.4 -58% -5% -22% -61% -6% -23% -62%

Diversions

Water use

Licensed private diverters 19.8 -20% 3% -2% -25% 3% -2% -25%



Urban supply 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 19.8 -20% 3% -2% -25% 3% -2% -25%


Sub-total 19.8 -20% 3% -2% -25% 3% -2% -25%

Outflows


To d/s McCoy's Bridge (EOS) 1585.2 -58% -5% -22% -62% -6% -23% -62%

River groundwater loss** 0.3 -57% -6% -20% -62% -4% -18% -60%

Sub-total 1585.6 -58% -5% -22% -62% -6% -23% -62%

Net evaporation*** 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 1585.6 -58% -5% -22% -62% -6% -23% -62%

Unattributed fluxes






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Reach 6 - Broken River to upstream of Casey's Weir





Storage volume

Change over period -0.1 210% 42% 53% 224% 44% 54% 225%

Inflows

Subcatchments

Directly gauged 108.4 -51% -3% -14% -47% -3% -14% -47%


Transfers from other basins 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 247.8 -51% -3% -15% -48% -3% -15% -48%

River groundwater gains* 0.0 -80% 79% -11% -90% 72% -18% -93%

Sub-total 247.8 -51% -3% -15% -48% -3% -15% -48%

Diversions

Water use

Licensed private diverters 1.9 -10% 6% 3% 3% 6% 3% 3%



Urban supply 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 1.9 -10% 6% 3% 3% 6% 3% 3%


Sub-total 1.9 -10% 6% 3% 3% 6% 3% 3%

Outflows


To d/s Broken River (Reach 8) 220.7 -54% -3% -16% -50% -3% -16% -51%

River groundwater loss 0.0 0% 0 0% 0% 0% 0% 0%

Sub-total 220.7 -54% -3% -16% -50% -3% -16% -51%

Net evaporation** 18.4 -33% 3% -3% -25% 2% -3% -26%

Sub-total 239.1 -52% -3% -15% -48% -3% -15% -49%

Unattributed fluxes

River unattributed loss 6.8 -40% -2% -7% -31% -3% -7% -32%


** Evaporation from private licensed storages (GL/year) is not included as it is already accounted in diversions


Appendix B

River m


Reach 7 - Broken River from Casey's Weir to Goulburn River confluence





Storage volume


Inflows

Subcatchments

Directly gauged 0.0 0% 0% 0% 0% 0% 0% 0%


From u/s Broken (Reach 7) 220.7 -54% -3% -16% -50% -3% -16% -51%

Sub-total 241.6 -53% -3% -16% -50% -3% -16% -50%

River groundwater gains* 0.0 -56% 23% -10% -70% 12% -22% -80%

Sub-total 241.6 -53% -3% -16% -50% -3% -16% -50%

Diversions

Water use

Licensed private diverters 12.2 -18% 3% 1% -10% 3% 1% -11%



Urban supply 0.1 -1% 0% 0% -1% 0% 0% -1%

Sub-total 18.5 -12% 2% 1% -7% 2% 0% -7%

Channel / pipe loss 0.1 -14% 6% 2% -4% 6% 2% -4%

Sub-total 18.6 -12% 2% 1% -7% 2% 0% -7%

Outflows


To Goulburn River 215.6 -58% -4% -17% -55% -4% -18% -55%

River groundwater loss** 0.0 -19% -21% -13% -2% -14% -4% 19%

Sub-total 215.6 -58% -4% -17% -55% -4% -18% -55%

Net evaporation*** 0.0 0% 0% 0% 0% 0% 0% 0%

Sub-total 215.6 -58% -4% -17% -55% -4% -18% -55%

Unattributed fluxes

River unattributed loss 7.4 -19% 0% -2% -15% 0% -3% -16%





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Appendix C River system model uncertainty assessment by reach

This Appendix contains the results of river reach water accounting for this region, as well as an assessment of the magnitude of the projected change under each scenario compared to the uncertainty associated with the river model. Each page provides information for a river reach that is bounded by a gauging station on the upstream and downstream side, and for which modelling results are available. Table C-1 provides a brief explanation for each component of the results page.

Table C-1. Explanation of components of the uncertainty assessments

Table Description Land use Information on the extent of dryland, irrigation and wetland areas.

Land use areas are based on remote sensing classification involving BRS land use mapping, water resources infrastructure and remote sensing-based estimates of actual evapotranspiration.

Gauging data Information on how well the river reach water balance is measured or, where not measured, can be inferred from observations and modelling. The volumes of water measured at gauging stations and off-takes is compared to the grand totals of all inflows or gains, and/or all outflows or losses, respectively. The ‘fraction of total’ refers to calculations performed on average annual flow components over the period of analysis. The ‘fraction of variance’ refers to the fraction of month-to-month variation that is measured. Also listed are the same calculations but for the sum of gauged terms plus water balance terms that could be attributed to the components listed in the ‘Water balance’ table with some degree of confidence. The same terms are also summed to water years and shown in the diagram next to this table.

Correlation with ungauged gains/losses

Information on the likely nature of ungauged components of the reach water balance. Listed are the coefficients of correlation between ungauged apparent monthly gains or losses on one hand, and measured components of the water balance on the other hand. Both the ‘normal’ (parametric) and the ranked (or non-parametric) coefficient of correlation are provided. High coefficients are highlighted. Positive correlations imply that the apparent gain or loss is large when the measured water balance component is large, whereas negative correlation implies that the apparent gain or loss is largest when the measured water balance component is small. In the diagram below this table, the monthly flows measured at the gauge at the end of the reach are compared with the flows predicted by the baseline river model, and the outflows that could be accounted for (i.e., the net result of all measured or estimated water balance components other than main stem outflow – which ideally should equal main stem outflows in order to achieve mass balance).

Water balance Information on how well the modelled and the best estimate river reach water balances agree, and what the nature of any unspecified losses in the river model is likely to be. The river reach water balance terms are provided as modelled by the baseline river model (Scenario A) over the period of water accounting. The accounted terms are based on gauging data, diversion records, and (adjusted) estimates derived from SIMHYD rainfall-runoff modelling, remote sensing of water use and simulation of temporary storage effects. Neither should be considered as absolutely correct, but large divergences point to large uncertainty in river modelling.

Model efficiency Information on the performance of the river model in explaining historic flow patterns at the reach downstream gauge, and the scope to improve on this performance. All indicators are based on the Nash-Sutcliffe model efficiency (NSME) indicator. In addition to the conventional NSME calculated for monthly and annual outflows, it has also been calculated after log-transformation or ranking of the original data, as well as having been calculated for the 10% of months with highest and lowest observed flows, respectively. Using the same formulas, the ‘model efficiency’ of the water accounts in explaining observed outflows is calculated. This provides an indication of the scope for improving the model to explain more of the observed flow patterns: if NSME is much higher for the water accounts than for the model, than this suggests that the model can be improved upon and model uncertainty reduced. Conversely, if both are of similar magnitude, then it is less likely that a better model can be derived without additional observation infrastructure.


AppendixC

Riversystem

modeluncertainty assessm

entbyreach

Table Description Change-uncertainty ratios

Information on the significance of the projected changes under different scenarios, considering the performance of the river model in explaining observed flow patterns at the end of the reach. In this table, the projected change is compared to the river model uncertainty by testing the hypothesis that the scenario model is about as good or better in explaining observed historic flows than the baseline model. The metric to test this hypothesis is the change-uncertainty ratio, which is calculated as the ratio of Nash-Sutcliffe Model Efficiency indicators for the scenario model and for the baseline (scenario A) model, respectively. A value of around 1.0 or less suggests that is likely that the projected scenario change is not significant when compared to river model uncertainty. Conversely, a ratio that is considerably greater than 1.0 implies that the scenario model is much worse in reproducing historic observations than the baseline model, which provides greater confidence that the scenario indeed leads to a significant change in flow patterns. The change-uncertainty ratio is calculated for monthly as well as annual values, to account for the possibility that the baseline model may reproduce annual patterns well but not monthly. Below this table on the left, the same information is provided in a diagram. Below the table on the right, the observed annual flows at the end of the reach is compared to those simulated by the baseline model and in the various scenarios. To the right of this table, the flow-duration curves are shown for all scenarios.


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Downstream gauge 404206 Broken @ Moorngag Reach 1Upstream gauge 404218 Broken @ Lake Nillahcootie

Reach length (km) 7.1Area (km2) 80Outflow/inflow ratio 2.20Net gaining reach

Land use ha %Dryland 8,046 100 Irrigable area - - Open water* - - River and wetlands - - Open water* - - * averages for 1990–2006

Gauging data Inflows Outflows Overalland gains and losses

Fraction of totalGauged 0.51 0.94 0.72Attributed 0.67 0.94 0.81Fraction of varianceGauged 0.93 0.98 0.95Attributed 0.94 0.98 0.96

Correlation with ungauged Gains Losses Linear adjustmentnormal ranked normal ranked

Main gauge inflows -0.11 -0.12 -0.24 -0.23Tributary inflows -0.09 -0.05 -0.73 -0.44Main gauge outflows -0.38 -0.76 -0.22 -0.15Distributary outflows - - - -Recorded diversions - - - -Estimated local runoff -0.04 -0.19 -0.31 -0.22

Water balance Model (A) Accounts Difference Model efficiency Model (A) AccountsJul 1990 – Jun 2006 MonthlyGains GL/y GL/y GL/y Normal 0.83 0.84Main stem inflows 55 30 24 Log-normalised - -Tributary inflows 0 5 -5 Ranked 0.29 <0Local inflows 18 12 6 Low flows only <0 <0Unattributed gains and noise - 23 -23 High flows only 0.73 0.74Losses GL/y GL/y GL/y AnnualMain stem outflows 68 67 1 Normal 0.97 0.74Distributary outflows 0 0 0 Log-normalised 0.93 <0Net diversions 0 0 0 Ranked 0.91 0.96River flux to groundwater 0 - 0River and floodplain losses 5 0 5 Definitions:Unspecified losses 0 - 0 - low flows (flows<10% percentile ) : 0.6 GL/moUnattributed losses and noise - 4 -4 - high flows (flows>90% percentile) : 16.5 GL/mo

-1 0 -1

Change-uncertainty ratiosP B Cwet Cmid Cdry Dwet Dmid Ddry

Annual streamflow 2.5 29.0 1.2 3.6 30.9 1.2 3.7 31.2Monthly streamflow 2.4 2.8 0.9 0.8 3.1 0.9 0.8 3.1

0.01

0.1

1

10

100

1000

0.01 0.1 1 10 100 1000

Annual Change-Uncertainty Ratio

Mon

thly

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Unc

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0

20

40

60

80

100

120

140

160

180

200

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Ann

ual s

tream

flow

(GL/

y)

gauged

A

P

B

Cwet

Cmid

Cdry

Dwet

Dmid

Ddry

0.001

0.01

0.1

1

10

100

0 20 40 60 80 100Pecentage of months flow is exceeded

Mon

thly

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amflo

w (G

L/m

o)

-250

-200

-150

-100

-50

0

50

100

150

200

250

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Rea

ch g

ains

and

loss

es (G

L/y)

unattributedgains

ungaugedgains

gaugedgains

unattributedlosses

ungaugedlosses

gaugedlosses

This is a strongly gaining reach. Flows are dominated by inflows from upstream

Most of the inflows are gauged. Estimated local runoff explains some of the ungauged gains. There are no recorded diversions and ungauged losses are small.

Baseline model performance is very good. Accounting also explains observed flows very well.

The projected changes are greater than river model uncertainty for the P, B, Cdry and Ddry scenarios, and slightly less for the monthly flows of the Cwet, Cmid, Dwet and Dmid scenarios.

P B C D+ wetO mid– dry

0.01

0.1

1

10

100

Jan-90 Jan-91 Jan-92 Jan-93 Jan-94 Jan-95 Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06

Mon

thly

stre

amflo

w (G

L/m

o)

gauged accounted model


AppendixC

Riversystem


entbyreach

Downstream gauge 404216 Broken @ Goorambat Reach 2Upstream gauge 404206 Broken @ Moorngag

Reach length (km) 39Area (km2) 1241Outflow/inflow ratio 3.51Net gaining reach

Land use ha %Dryland 115,518 93 Irrigable area - - Open water* - - River and wetlands 8,610 7 Open water* - - * averages for 1990–2006





Water balance Model (A) Accounts Difference Model efficiency Model (A) AccountsJul 1990 – Jun 2006 MonthlyGains GL/y GL/y GL/y Normal <0 0.04Main stem inflows 68 67 1 Log-normalised 0.27 0.27Tributary inflows 0 16 -16 Ranked 0.15 0.16Local inflows 163 138 24 Low flows only <0 <0Unattributed gains and noise - 111 -111 High flows only <0 <0Losses GL/y GL/y GL/y AnnualMain stem outflows 210 234 -24 Normal <0 <0Distributary outflows 0 0 0 Log-normalised <0 0.07Net diversions 2 0 2 Ranked <0 <0River flux to groundwater 0 - 0River and floodplain losses 13 19 -6 Definitions:Unspecified losses 6 - 6 - low flows (flows<10% percentile ) : 0.9 GL/moUnattributed losses and noise - 78 -78 - high flows (flows>90% percentile) : 58.4 GL/mo

0 0 0



0.01

0.1

1

10

100

1000

0.01 0.1 1 10 100 1000


Mon

thly

Cha

nge-

Unc

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Rat

io

0

100

200

300

400

500

600

700

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Ann

ual s

tream

flow

(GL/

y)

gauged

A

P

B

Cwet

Cmid

Cdry

Dwet

Dmid

Ddry

0.001

0.01

0.1

1

10

100

1000


Mon

thly

stre

amflo

w (G

L/m

o)

-800

-600

-400

-200

0

200

400

600

800

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Rea

ch g

ains

and

loss

es (G

L/y)

unattributedgains

ungaugedgains

gaugedgains

unattributedlosses

ungaugedlosses

gaugedlosses

This is a strongly gaining reach. Flows are dominated by inflows from upstream and runoff immediately following rain.

Few of the inflows are gauged. Estimated local runoff explains some of the ungauged gains. There are no recorded diversions and ungauged losses are moderate

Baseline model performance is poor. Accounting is also poor.

The projected changes are similar to or less than river model uncertainty.


0.1

1

10

100

1000


Mon

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L/m

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Downstream gauge 405201 Goulburn @ Trawool Reach 3Upstream gauge 405203 Goulburn @ Eildon Dam







Water balance Model (A) Accounts Difference Model efficiency Model (A) AccountsJul 1990 – Jun 2006 MonthlyGains GL/y GL/y GL/y Normal <0 0.96Main stem inflows 0 1401 -1401 Log-normalised - -Tributary inflows 0 5 -5 Ranked <0 0.96Local inflows 0 737 -737 Low flows only <0 <0Unattributed gains and noise - 125 -125 High flows only <0 0.96Losses GL/y GL/y GL/y AnnualMain stem outflows 0 2224 -2224 Normal <0 0.94Distributary outflows 0 0 0 Log-normalised - -Net diversions 0 0 0 Ranked <0 0.93River flux to groundwater 0 - 0River and floodplain losses 0 0 0 Definitions:Unspecified losses 0 - 0 - low flows (flows<10% percentile ) : 56.0 GL/moUnattributed losses and noise - 44 -44 - high flows (flows>90% percentile) : 297.4 GL/mo

0 0 0


Annual streamflowMonthly streamflow

0.01

0.1

1

10

100

1000

0.01 0.1 1 10 100 1000


Mon

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Rat

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gauged

0

500

1000

1500

2000

2500

3000

3500

4000

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Ann

ual s

tream

flow

(GL/

y)

0.001

0.01

0.1

1

10

100

1000

0 20 40 60 80 100

Pecentage of months flow is exceeded

Mon

thly

stre

amflo

w (G

L/m

o)

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Rea

ch g

ains

and

loss

es (G

L/y)

unattributedgains

ungaugedgains

gaugedgains

unattributedlosses

ungaugedlosses

gaugedlosses

This is a gaining reach. Flows are dominated by inflows from upstream and runoff immediately following rain.

Most of the inflows are gauged. Estimated local runoff explains most of the ungauged gains. There are no recorded diversions and ungauged losses are small.

No model results were available. Accounting also explains observed flows extremely well.

10

100

1000


Mon

thly

stre

amflo

w (G

L/m

o)

gauged accounted


AppendixC

Riversystem


entbyreach

Downstream gauge 405202 Goulburn @ Seymour Reach 4Upstream gauge 405202 Goulburn @ Trawool






Main gauge inflows -0.51 -0.16 -0.29 -0.42Tributary inflows -0.77 -0.81 -0.22 -0.43Main gauge outflows -0.62 -0.24 -0.19 -0.36Distributary outflows - - - -Recorded diversions - - - -Estimated local runoff -0.92 -0.68 -0.38 -0.61 Adjusted -95.0%

Water balance Model (A) Accounts Difference Model efficiency Model (A) AccountsJul 1990 – Jun 2006 MonthlyGains GL/y GL/y GL/y Normal <0 0.98Main stem inflows 0 2224 -2224 Log-normalised - -Tributary inflows 0 5 -5 Ranked <0 0.99Local inflows 0 6 -6 Low flows only <0 0.93Unattributed gains and noise - 58 -58 High flows only <0 0.98Losses GL/y GL/y GL/y AnnualMain stem outflows 0 2236 -2236 Normal <0 0.99Distributary outflows 0 0 0 Log-normalised - -Net diversions 0 0 0 Ranked <0 0.99River flux to groundwater 0 - 0River and floodplain losses 0 0 0 Definitions:Unspecified losses 0 - 0 - low flows (flows<10% percentile ) : 57.0 GL/moUnattributed losses and noise - 58 -58 - high flows (flows>90% percentile) : 293.2 GL/mo

0 0 0


Annual streamflowMonthly streamflow

0.01

0.1

1

10

100

1000

0.01 0.1 1 10 100 1000


Mon

thly

Cha

nge-

Unc

erta

inty

Rat

io

gauged

0

500

1000

1500

2000

2500

3000

3500

4000

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Annu

al s

tream

flow

(GL/

y)

0.001

0.01

0.1

1

10

100

1000

10000

0 20 40 60 80 100

Pecentage of months flow is exceeded

Mon

thly

stre

amflo

w (G

L/m

o)

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Rea

ch g

ains

and

loss

es (G

L/y)

unattributedgains

ungaugedgains

gaugedgains

unattributedlosses

ungaugedlosses

gaugedlosses

This neither a gaining nor losing reach. Flows are dominated by inflows from upstream.

Most of the inflows are gauged. There are no recorded diversions and ungauged losses are small.

No model results were available. Accounting explains observed flows extremely well.

10

100

1000


Mon

thly

stre

amflo

w (G

L/m

o)

gauged accounted


App

endi

x C

Riv

er s

yste

m m

odel

unc

erta

inty

ass

essm

ent b

y re

ach

Downstream gauge 405200 Goulburn @ Murchison Reach 5Upstream gauge 405202 Goulburn @ Seymour

Reach length (km) 67Area (km2) 1412Outflow/inflow ratio 0.34Net losing reach





Main gauge inflows -0.64 -0.18 -0.12 -0.22Tributary inflows -0.74 -0.43 -0.10 -0.29Main gauge outflows -0.87 -0.37 -0.11 -0.04Distributary outflows - - - -Recorded diversions -0.28 -0.29 -0.25 -0.32Estimated local runoff -0.81 -0.42 -0.12 -0.31 Adjusted 26.1%

Water balance Model (A) Accounts Difference Model efficiency Model (A) AccountsJul 1990 – Jun 2006 MonthlyGains GL/y GL/y GL/y Normal 0.95 0.99Main stem inflows 1391 2236 -845 Log-normalised 0.61 #NUM!Tributary inflows 0 65 -65 Ranked 0.27 0.65Local inflows 1099 86 1013 Low flows only <0 <0Unattributed gains and noise - 26 -26 High flows only 0.97 0.99Losses GL/y GL/y GL/y AnnualMain stem outflows 845 761 84 Normal 0.97 0.99Distributary outflows 0 0 0 Log-normalised 0.91 0.94Net diversions 1491 1563 -72 Ranked 0.95 0.94River flux to groundwater 0 - 0River and floodplain losses 7 7 0 Definitions:Unspecified losses 147 - 147 - low flows (flows<10% percentile ) : 8.7 GL/moUnattributed losses and noise - 82 -82 - high flows (flows>90% percentile) : 192.0 GL/mo

0 0 0



0.01

0.1

1

10

100

1000

0.01 0.1 1 10 100 1000


Mon

thly

Cha

nge-

Unc

erta

inty

Rat

io

0

500

1000

1500

2000

2500

3000

3500

4000

4500

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Annu

al s

tream

flow

(GL/

y)

gauged

A

P

B

Cwet

Cmid

Cdry

Dwet

Dmid

Ddry

0.001

0.01

0.1

1

10

100

1000

10000


Mon

thly

stre

amflo

w (G

L/m

o)

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Rea

ch g

ains

and

loss

es (G

L/y)

unattributedgains

ungaugedgains

gaugedgains

unattributedlosses

ungaugedlosses

gaugedlosses

This is a strongly losing reach. Flows are dominated by inflows from upstream.

Most of the inflows are gauged. There are large recorded diversions and ungauged losses are small.

Baseline model performance is excellent. Accounting explains observed flows moderately well.

The projected changes are greater than river model uncertainty for all scenarios and much greater for P, B, Cdry and Ddry scenarios.


1

10

100

1000


Mon

thly

stre

amflo

w (G

L/m

o)



AppendixC

Riversystem


entbyreach

Downstream gauge 405204 Goulburn @ Shepparton Reach 6Upstream gauge 405201 Goulburn @ Murchison






Main gauge inflows -0.84 -0.47 -0.10 -0.19Tributary inflows -0.18 -0.04 -0.76 -0.57Main gauge outflows -0.90 -0.63 -0.10 -0.03Distributary outflows - - - -Recorded diversions -0.00 #DIV/0! -0.00 #DIV/0!Estimated local runoff -0.84 -0.50 -0.06 -0.07 Adjusted -19.5%

Water balance Model (A) Accounts Difference Model efficiency Model (A) AccountsJul 1990 – Jun 2006 MonthlyGains GL/y GL/y GL/y Normal 0.96 0.95Main stem inflows 845 761 84 Log-normalised 0.76 0.81Tributary inflows 0 234 -234 Ranked 0.40 0.69Local inflows 419 195 224 Low flows only <0 <0Unattributed gains and noise - 144 -144 High flows only 0.95 0.85Losses GL/y GL/y GL/y AnnualMain stem outflows 1246 1179 67 Normal 0.98 0.95Distributary outflows 0 0 0 Log-normalised 0.94 0.89Net diversions 17 13 4 Ranked 0.98 0.98River flux to groundwater 0 - 0River and floodplain losses 0 0 0 Definitions:Unspecified losses 0 - 0 - low flows (flows<10% percentile ) : 13.0 GL/moUnattributed losses and noise - 156 -156 - high flows (flows>90% percentile) : 281.1 GL/mo

0 -13 13



0.01

0.1

1

10

100

1000

0.01 0.1 1 10 100 1000


Mon

thly

Cha

nge-

Unc

erta

inty

Rat

io

0

1000

2000

3000

4000

5000

6000

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Annu

al s

tream

flow

(GL/

y)

gauged

A

P

B

Cwet

Cmid

Cdry

Dwet

Dmid

Ddry

0.001

0.01

0.1

1

10

100

1000

10000


Mon

thly

stre

amflo

w (G

L/m

o)

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Rea

ch g

ains

and

loss

es (G

L/y)

unattributedgains

ungaugedgains

gaugedgains

unattributedlosses

ungaugedlosses

gaugedlosses

This is a gaining reach. Flows are dominated by inflows from upstream and runoff immediately following rain.

Most of the inflows are gauged. Estimated local runoff explains most of the ungauged gains but a moderate adjustment was required. There are some recorded diversions and ungauged losses are small.

Baseline model performance is excellent. Accounting also explains observed flows extremely well.

The projected changes are greater than river model uncertainty for all scenarios, and much greater for P, B, Cdry and Dry scenarios.


1

10

100

1000

10000


Mon

thly

stre

amflo

w (G

L/m

o)



App

endi

x C

Riv

er s

yste

m m

odel

unc

erta

inty

ass

essm

ent b

y re

ach

Downstream gauge 405232 Goulburn @ McCoy Bridge Reach 7Upstream gauge 405204 Goulburn @ Shepparton

Reach length (km) 50Area (km2) 459Outflow/inflow ratio 0.99Net losing reach





Main gauge inflows -0.12 -0.02 -0.66 -0.51Tributary inflows - - - -Main gauge outflows -0.19 -0.19 -0.58 -0.43Distributary outflows - - - -Recorded diversions - - - -Estimated local runoff -0.03 -0.00 -0.61 -0.35 Adjusted -90.0%

Water balance Model (A) Accounts Difference Model efficiency Model (A) AccountsJul 1990 – Jun 2006 MonthlyGains GL/y GL/y GL/y Normal 0.92 0.98Main stem inflows 1246 1179 67 Log-normalised 0.75 0.98Tributary inflows 0 0 0 Ranked 0.36 0.94Local inflows 23 1 22 Low flows only <0 <0Unattributed gains and noise - 60 -60 High flows only 0.90 0.94Losses GL/y GL/y GL/y AnnualMain stem outflows 1262 1163 99 Normal 0.97 1.00Distributary outflows 0 0 0 Log-normalised 0.95 0.99Net diversions 8 0 8 Ranked 0.97 0.99River flux to groundwater 0 - 0River and floodplain losses 0 17 -17 Definitions:Unspecified losses 0 - 0 - low flows (flows<10% percentile ) : 14.6 GL/moUnattributed losses and noise - 60 -60 - high flows (flows>90% percentile) : 299.0 GL/mo

-1 0 -1



0.01

0.1

1

10

100

1000

0.01 0.1 1 10 100 1000


Mon

thly

Cha

nge-

Unc

erta

inty

Rat

io

0

1000

2000

3000

4000

5000

6000

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Ann

ual s

tream

flow

(GL/

y)

gauged

A

P

B

Cwet

Cmid

Cdry

Dwet

Dmid

Ddry

0.001

0.01

0.1

1

10

100

1000

10000


Mon

thly

stre

amflo

w (G

L/m

o)

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

0

00/0

1

01/0

2

02/0

3

03/0

4

04/0

5

05/0

6

Rea

ch g

ains

and

loss

es (G

L/y)

unattributedgains

ungaugedgains

gaugedgains

unattributedlosses

ungaugedlosses

gaugedlosses

This is neither a gaining nor losing reach. Flows are dominated by inflows from upstream.

Most of the inflows are gauged. There are no recorded diversions and ungauged losses are small.

Baseline model performance is excellent. Accounting also explains observed flows extremely well.

The projected changes are greater than river model uncertainty for all scenarios, though only slightly greater for the Cwet and Dwet scenarios.


1

10

100

1000

10000


Mon

thly

stre

amflo

w (G

L/m

o)


Enquiries

More information about the project can be found at www.csiro.au/mdbsy. This information includes the full terms of reference for the project, an overview of the project methods and the project reports that have been released to-date.

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