Background report on the Great Artesian Basin€¦ · Background report on the Great Artesian Basin A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable

A.L. Herczeg

September 2008

Background report on the Great Artesian BasinA 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.

Acknowledgments

Richard Cresswell and Ray Evans are thanked for providing a review of the report. Assistance with figures and data by Phil Davies and

Vic Waclawik is also gratefully acknowledged.

Citation

Herczeg AL (2008) Background report on the Great Artesian Basin. A report to the Australian Government from the CSIRO Murray-

Darling Basin Sustainable Yields Project. CSIRO, Australia. 18pp.

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

Preface

This is a report to the Australian Government from CSIRO. It is an output of the Murray-Darling Basin Sustainable Yields

Project which assessed current and potential future water availability in 18 regions across the Murray-Darling Basin

(MDB) considering climate change and other risks to water resources. The project was commissioned following the

Murray-Darling Basin Water Summit convened by the then Prime Minister of Australia in November 2006 to report

progressively during the latter half of 2007. The reports for each of the 18 regions and for the entire MDB are supported

by a series of technical reports detailing the modelling and assessment methods used in the project. This report is one of

the supporting technical reports of the project. Project reports can be accessed at http://www.csiro.au/mdbsy.

Project findings are expected to inform the establishment of a new sustainable diversion limit for surface and

groundwater in the MDB – one of the responsibilities of a new Murray-Darling Basin Authority in formulating a new

Murray-Darling Basin Plan, as required under the Commonwealth Water Act 2007. These reforms are a component of

the Australian Government’s new national water plan ‘Water for our Future’. Amongst other objectives, the national water

plan seeks to (i) address over-allocation in the MDB, helping to put it back on a sustainable track, significantly improving

the health of rivers and wetlands of the MDB and bringing substantial benefits to irrigators and the community; and (ii)

facilitate the modernisation of Australian irrigation, helping to put it on a more sustainable footing against the background

of declining water resources.

© CSIRO 2008 Background report on the Great Artesian Basin

Table of Contents

1 Summary ................................................................................................................................... 1

2 Introduction............................................................................................................................... 2 2.1 Background..................................................................................................................................................................2 2.2 Objectives ....................................................................................................................................................................6 2.3 Definition of the Great Artesian Basin for this project ....................................................................................................6

3 Previous work in New South Wales......................................................................................... 7

4 Previous work in Queensland ............................................................................................... 11

5 Connectivity to surface water systems................................................................................ 12 5.1 Connectivity................................................................................................................................................................12 5.2 Groundwater use in Great Artesian Basin aquifers .....................................................................................................14 5.3 Interactions with water sharing plans..........................................................................................................................14

6 Key messages......................................................................................................................... 15

7 References .............................................................................................................................. 16

8 Appendix................................................................................................................................. 17 8.1 Data from the groundwater management units of the Great Artesian Basin with reference to water allocation and current use..............................................................................................................................................................................17

Figures

Figure 2-1. Water pressure difference between the Jurassic and watertable aquifers (from Evans et al., 1995) ...............................3 Figure 2-2. Location of the Great Artesian Basin Intake Beds, the Great Artesian Basin, Jurassic aquifers and regions defined for this project .......................................................................................................................................................................................4 Figure 2-3. Schematic cross section showing the relationship between Great Artesian Basin aquifers and the alluvium and surface drainages in the Darling, Warrego and Paroo rivers (Ife and Skelt, 2004) ........................................................................................5 Figure 2-4. Schematic cross section showing the relationship between Great Artesian Basin aquifers and the alluvium and surface drainages in the Condamine-Balonne region (Ife and Skelt, 2004)...................................................................................................5 Figure 3-1. Map showing the inferred recharge zone and remainder of the Coonamble Embayment (after DWR (1991) as cited in Brownbill (2000)) .............................................................................................................................................................................7 Figure 3-2. Map showing the geological formations, topography and present day potentiometric head of the Pilliga Sandstone within the Coonamble Embayment (after Wolfgang, 2000)...............................................................................................................9 Figure 3-3. Flood map showing boundaries of a major flood in the Macquarie and Castlereagh catchments (after DWR, 1991) ....10 Figure 5-1. Map showing Great Artesian Basin Intake Beds and Great Artesian Basin Jurassic aquifer system and losing and gaining streams within the Darling River Basin ..............................................................................................................................13

Background report on the Great Artesian Basin © CSIRO 2008

1 Summary

The Great Artesian Basin (GAB) occupies one-fifth of Australia and underlies a large portion of the Darling River Basin

(DRB). Interactions between the main water-bearing aquifers (Jurassic or J-aquifer) of the GAB and the DRB are related

to the upward pressures exerted by the GAB in central and western New South Wales and Queensland, and leakage

from surface drainage and alluvial systems of the DRB to the GAB Intake Beds situated in the western slopes of the

Great Dividing Range. The purpose of this report is to provide background hydrogeological information on the GAB

groundwater systems in the southeastern part of the basin where the water allocation and water sharing plans of the

GAB may have potential impact on the DRB surface water and aquifer systems. The focus is on regions where

connectivity is established and where changes in water use may impact on the latter estimates of long-term extraction

limits.

The influence of the GAB on the surface water systems or watertable aquifers that are interconnected to the streams

may take several forms:

• direct leakage of DRB tributaries to the GAB Jurassic-Cretaceous (J-K) units through outcrop areas

• leakage of water to the GAB from DRB alluvial aquifers where it has a higher hydraulic head than the J-K units

• discharge of water from the J-K units either into the river systems via artesian springs, or to the DRB alluvial

aquifers

• extraction of water from J-K units via artesian wells or pumping may induce leakage of streams or alluvial

aquifers through reduced upward pressure gradients

• discharge of uncontrolled bore drains into watertable aquifers or diversion to surface water tributaries

• captured discharge in the intake beds where pumping causes the hydraulic gradient to rivers to lessen

(diminution of rejected recharge).

The most significant areas of interaction between the GAB intake areas and surface waters are in the Macquarie-

Castlereagh region of New South Wales (Region 8), Border Rivers region of New South Wales and Queensland (Region

5), and the Condamine-Balonne region of Queensland (Region 3) where the regions traverse the intake beds of the GAB

in their middle reaches. Of lesser significance are the Warrego, Gwydir and Namoi regions (regions 2, 6 and 7). Current

and proposed water extraction limits of the GAB water sharing plan are likely to reduce baseflow in these areas in the

DRB. Interventions such as the GAB bore rehabilitation program will likely have little impact on the DRB systems in New

South Wales because of time lags between bore rehabilitation actions and attainment of new equilibrium bore pressures

by virtue of large distances from the artesian bores and the intake beds and corresponding impacts on connectivity with

surface water systems.

© CSIRO 2008 Background report on the Great Artesian Basin ▪ 1

2 Introduction

2.1 Background

The Great Artesian Basin (GAB) underlies about one-fifth of the Australian continent, including large parts of Queensland

and northern New South Wales. It contains about 8.7 x 106 GL of water in storage (GABCC, 1998) with groundwater

ages up to 2 million years in the central portion of the basin near the South Australia–Queensland border. The

hydrogeology and hydrochemistry of the basin has been described in considerable detail (Habermehl, 1980, 1997;

Herczeg et al., 1991; Habermehl and Lau, 1997; Radke et al., 2000) and summarised in the Great Artesian Basin

Strategic Plan available on the Great Artesian Basin Coordinating Committee (GABCC) website

(http://www.gabcc.org.au/index.aspx).

Total recharge area of the basin is estimated to be about 10% of the total area with an annual recharge volume of 1000

GL/year. This translates to an estimated average basin-wide recharge rate of between 1–2% of rainfall (~5–10 mm/year).

However, this rate varies from place to place depending on vegetation, soil type and extent of surface drainage.

Recharge occurs near the GAB boundaries through the intake beds and vertical infiltration via overlying alluvial aquifers

along the western slopes of the Great Dividing Range1. Recharge is thought to occur in the eastern margin areas through

local diffuse recharge and in part through direct infiltration from streams. Groundwater flows westward, south-westward

and southward from the eastern margin of the GAB portion that lies within the DRB to discharge areas that are

manifested as springs, leakage to alluvial aquifers, diffuse discharge to inland salt playa lakes and artesian bores.

The main water-bearing aquifers (the Jurassic–Lower Cretaceous sandstone units, known generally as the ‘J aquifer’ or

‘J-K’ aquifers) within the GAB underlie about 40% of the DRB, primarily in the north-west (Error! Reference source not

found.). The map shows the relative head difference between the main GAB aquifer and the watertable aquifers in the

DRB. For the most part, the GAB has an upward head gradient except in the highlighted stippled areas which are the

intake beds of the GAB and where the J-aquifer has a lower piezometric head than the alluvial aquifers. For the majority

of the area the GAB is confined and has a higher potentiometric head than the watertable aquifers.

The New South Wales portion of the recharge zone of the GAB is largely located within the Coonamble Embayment and

may not be connected to the larger continental scale GAB aquifer system. Discharge occurs via springs and possibly via

upward leakage to streams in the lower reaches of the Macquarie, Bogan and Barwon rivers (Evans et al., 1995; Radke

et al., 2000).


Castlereagh region of New South Wales (Region 8), Border Rivers region of New South Wales and Queensland (Region

5), and the Condamine-Balonne region of Queensland (Region 3) where the regions traverse the intake beds of the GAB

in their middle reaches. Of lesser significance are the areas in the Warrego, Gwydir and Namoi regions (regions 2, 6 and

7) (Figure 2-2). Contribution of the GAB to baseflow potentially exists in the central and western DRB, but this is

controlled by the extent and thickness of the impermeable confining shale layers between the GAB Jurassic system and

the GAB alluvium (Figure 2-3 and Figure 2-4).

1 Recharge also occurs along the western margin of the GAB in South Australia and the Northern Territory, but the flow systems emanating from that area are not relevant to this study.

2 ▪ Background report on the Great Artesian Basin © CSIRO 2008

Figure 2-1. Water pressure difference between the Jurassic and watertable aquifers (from Evans et al., 1995)


Figure 2-2. Location of the Great Artesian Basin Intake Beds, the Great Artesian Basin, Jurassic aquifers and

regions defined for this project


Figure 2-3. Schematic cross section showing the relationship between Great Artesian Basin aquifers and the alluvium and surface

drainages in the Darling, Warrego and Paroo rivers (Ife and Skelt, 2004)

Figure 2-4. Schematic cross section showing the relationship between Great Artesian Basin aquifers and the alluvium and surface

drainages in the Condamine-Balonne region (Ife and Skelt, 2004)


2.2 Objectives

The purpose of this report is to (i) provide background material on the connectivity between the GAB aquifers and the

surface water and/or alluvial systems of the DRB, and (ii) evaluate the potential impact of extraction from the GAB

aquifers on changes to the level of connectivity and assumptions used in the catchment water assessments at the

various tiers of reporting. These three tiers are (i) impacts on stream recharge, (ii) groundwater recharge and pumping,

and (iii) connectivity and leakage between the DRB and the GAB. Given the scope and information currently available,

this is not intended as a comprehensive assessment, which would be a major task, but attempts to identify where

impacts may be important and require follow-up investigation.

The influence of the GAB on the surface water systems or watertable aquifers that are interconnected to the streams

may take several forms:

• direct leakage of DRB tributaries to the GAB J-K units through outcrop areas

• leakage of water to the GAB from DRB alluvial aquifers where it has a higher hydraulic head than the J-K units

• discharge of water from the J-K units either into the river systems via artesian springs, or to the DRB alluvial

aquifers

• extraction of water from J-K units via artesian wells or pumping may induce leakage of streams or alluvial

aquifers through reduced upward pressure gradients

• discharge of uncontrolled bore drains into watertable aquifers or diversion to surface water tributaries

• captured discharge in the intake beds where pumping causes the hydraulic gradient to rivers to lessen

(diminution of rejected recharge).

2.3 Definition of the Great Artesian Basin for this project

The distinction between the sediments of the DRB and those of the GAB is somewhat arbitrary. The adopted working

definitions vary from state to state, because states manage aquifers on the basis of groundwater management units

(GMUs) that are based on local jurisdictions or surface water catchment management boundaries. This is further

complicated by the four categories that refer to the GAB system:

• GAB Jurassic, which represents the main high quality water yielding Jurassic (and in some places Lower

Cretaceous) formations known variously as the Pilliga Sandstone (in the Coonamble Embayment), Hooray

Sandstone and Cadna-owie Formation

• GAB Alluvial, which are the sedimentary units close to the surface and may be part of the DRB Quaternary

sediments

• GAB Cap Rock, which represents the surficial part of the GAB which is characterised by calcrete deposits or

low permeable layers

• GAB Intake Beds, which are the areas at the margin of the GAB that accept direct and indirect recharge through

outcrop of the main water-bearing systems and are unconfined and may have substantial unsaturated zones.


3 Previous work in New South Wales

The area of the GAB that is within New South Wales is ~207 000 km2 (~11 percent of the GAB). The area includes part

of the Coonamble Embayment, lies in the New South Wales portion of the GAB, and is located west of the

Warrumbungle Ranges (Figure 3-1). The general topography declines from 300 m in the east at the foot of the

Warrumbungle Ranges to ~125 m at Carinda in the north-west (Figure 3-2). The main productive aquifers are the

Jurassic Pilliga Sandstone which outcrops at higher elevations further to the east (250 to 600 m) and the Hooray

Sandstone. Most of the surficial cover in the area is classified as undifferentiated Quaternary cover.

Rainfall is ~900 mm in the south-east (uplands) to <400 mm in the north-west. In general it is 450 to 550 mm throughout

most of the area, dominated slightly by summer rainfall but also with significant winter rainfall. Rainfall trends are

markedly drier in the first half of the 20th century compared to the second half of the century as is commonly observed in

south-east Australia. Annual potential evapotranspiration ranges from 1300 mm in the east to 2000 mm in the west.

Figure 3-1. Map showing the inferred recharge zone and remainder of the Coonamble Embayment (after DWR (1991) as cited in

Brownbill (2000))

The area considered incorporates the Macquarie-Castlereagh, Namoi, Gwydir and Border Rivers catchments of northern

New South Wales which are part of the larger DRB. These areas include development for cotton, grazing and other

cropping systems and use significant quantities of GAB water for irrigation. The region includes the Ramsar-listed

Macquarie Marshes that may be affected by upward GAB artesian pressure that in turn increases the head and

consequent discharge to streams from the phreatic aquifers.

The existing conceptual model for recharge to the GAB is to the Pilliga and Mooga sandstone aquifer along the western

slopes of the Great Dividing Range. In the south, recharge occurs through alluvial fans on the Warrumbungle Ranges in

the south and east portions of the Coonamble Embayment. Groundwater moves in a north and northwesterly direction

along a low gradient. The range in estimates of Darcy flow velocity is from 0.1 to 0.8 m/year. There are estimated to be

~6000 bores in the entire area in both the phreatic and artesian systems. Mean pressure from the Pilliga Sandstone

aquifer dropped from 180 to 145 m by 1935, with a relatively slow decline since then to the present (Brownbill, 2000).


There have been several attempts to estimate recharge rate to the Coonamble Embayment within the New South Wales

portion of the GAB. These estimates have ranged over two orders of magnitude. An estimate of 190 GL/year (assuming

uniform recharge of 6 mm/year throughout the defined area of recharge) based on chloride mass balance (Wolfgang,

2000) is somewhat lower than previous estimates for the GAB in the Coonamble zone. The recharge rates quoted for the

GAB are for the long-term flux to the confined aquifer and do not include recharge that is later rejected from the intake

beds back to the local river system. That is, the recharge rates quoted are relevant to long-term sustainability of GAB

resource management.

Discharge is thought to be predominantly within several areas of mound springs, about one-third of which are extinct,

located at the western edge of the embayment. A group of mound springs located north and north-east of Bourke are

thought to be derived from flow systems originating from Queensland. It is not clear whether the mound springs were

active prior to development of the basin after the late 1800s.

The general view is that the Coonamble Embayment is an isolated part of the GAB rather than connected as a whole.

That is, recharge and discharge occurs within the embayment and little water, if any, flows outside to the other states or

to western New South Wales where flow systems within the GAB are derived from recharge areas in Queensland

roughly in a line from latitude 22 to 24 °S.

The first artesian bores tapping the GAB aquifers were developed in the late 1880s and a number of weirs were

constructed along the Macquarie River in the 1890s. The early 1900s saw a rapid increase in rate of development. Major

land clearing in the eastern and southern portion is thought to have caused rising watertables and dryland salinity and

streambank erosion.


Figure 3-2. Map showing the geological formations, topography and present day potentiometric head of the Pilliga Sandstone within the

Coonamble Embayment (after Wolfgang, 2000)

There has been an estimated pressure loss over 80% of the New South Wales portion of the GAB and now less than

50% of the total New South Wales portion of the GAB has artesian pressures. Decrease in pressure had already been

noticed in 1893. The pressure head near the recharge zone, west of the Warrumbungle Ranges, was ~200 m (pre-1910)

and declined to ~160 m in the mid-1980s (Wolfgang, 2000). In the north-west Coonamble Embayment the pressure head

has fallen from 150 to 130 m while in the south-east it has fallen from 230 to 160 m. The greatest rate of change was

observed from 1900 to 1920.

The most recent studies of the water fluxes, water balance and recharge of the GAB within the Coonamble Embayment

are by Brownbill (2000) and Wolfgang (2000). The former report considers the groundwater status of the region with

respect to analysis of hydrographs and potential impacts of irrigation, land-use change and surface water diverions. The

Pilliga Sandstone has been exploited since the early 1900s and significant declines in hydraulic pressure were noted at

least 50 years ago when the News South Wales government started monitoring key artesian bores regularly.

The 36Cl data for the New South Wales portion of the GAB indicate flow systems increasing in age along the inferred

hydraulic gradient, with indicative groundwater ages ranging from less than 5,000 years, within the highland areas and


river alluvial valleys in the recharge zone, to greater than 200,000 years, in the western part of the Coonamble

Embayment (Radke et al., 2000). The inferred horizontal flow rates are 4 m/year in the alluvial fans that abut the Great

Dividing Range, decreasing to less than 1 m/year as groundwater traverses towards the plains.

The importance of flooding events to the recharge of the Pilliga Sandstone is not certain. There are claims, however, of

its importance being far greater than that of diffuse widespread recharge (Keshwan, 1995). Wolfgang (2000), on the

other hand, suggests that its importance is overstated due to the Pilliga Sandstone having a greater head than the river

systems in the larger portion of the flooded river valley areas. Periodic flooding occurs along the river valleys of the

Macquarie and Castlereagh rivers, although the extent and frequency of flooding has declined due to the dams and

impoundments built along the Macquarie River in the 20th century. There are reportedly records of ten or more floods in

the region (Keshwan, 1995) with up to ~25% of the area flooded and about three to four major floods per century. The

last major floods were in the 1950s and 1970s (the latter Castlereagh flood only due to the dams on the Macquarie).

Figure 3-3. Flood map showing boundaries of a major flood in the Macquarie and Castlereagh catchments (after DWR, 1991)

The extinct or ‘palaeo’ mound springs along the northern Bogan River imply wetter conditions at some time in the past

resulting in higher artesian pressures. It is not established whether discharge from the artesian bores has lowered the

pressure leading to the decrease in mound spring discharge or whether the mound springs were inactive prior to

development.. Most are reported to be not flowing now but may have been active until the early 20th century.


4 Previous work in Queensland

Kellett et al. (2003) provide the most comprehensive overview of the recharge processes to the GAB in Queensland and

the connection with surface water systems. Subsequently Australian Groundwater and Environmental consultants (AGE)

have assessed interactions between surface water and groundwater systems of the GAB in Queensland (AGE, 2005).

Kellett et al. (2003) identified the Warrego River north-east of Augathella, the Maranoa River north of Mitchell, and the

Weir River/Western Creek west of Toowoomba as being directly connected with the GAB Intake Beds. Very low chloride

concentrations in GAB groundwater within the intake beds located in the upper reaches of the Maranoa and Warrego

rivers are thought to be caused by direct infiltration from the surface water systems. Current extraction from the Hooray

aquifer of the GAB in the area between Miles and Mitchell is estimated to be 50% of recharge and changes in that level

are likely to have an impact on surface water tributary flows.

The AGE report (AGE, 2005) has identified a number of reaches of rivers and streams in the Warrego, Condamine,

Balonne, Moonie and Border Rivers systems where baseflow is derived from the GAB. The report does not identify

localised recharge to the GAB aquifers from the surface water systems.


5 Connectivity to surface water systems

5.1 Connectivity

It is reported by Brownbill (2000) that there is connectivity between the Jurassic GAB aquifer and the overlying Cainozoic

aquifer. This has been inferred by changes in pressure of the Mesozoic GAB system in reponse to pumping, infiltration

and evapotranspiration from the overlying Cainozoic system. Brownbill considered that there is a need to obtain better

estimates of recharge in the Border Rivers/intake beds region where there is also extensive groundwater extraction.

Radke et al. (2000) also suggest that the Cainozoic aquifer recharges Pilliga Sandstones in the northern part of the study

area where the head gradient is higher and where the chemistry of the two systems are similar.

The GAB Intake Beds have been assigned a zero connectivity rate in New South Wales. This connectivity rate is

assumed within the context of the very low recharge rates assigned to the intake beds (about 0.5% of rainfall). The low

recharge rates are derived within the context that ‘recharge is often rejected back to the surface for stream baseflow’

(RM Williams, pers. comm.). The low connectivity may be thought to apply to the intake beds only after the recharge is

rejected as this is the more robust estimate of long-term recharge to the GAB confined aquifers. The recharge rates

referred to above have been estimated for management of the regional confined GAB aquifers. It is assumed that these

aquifers have no connectivity with the surface water systems of the basin. However, the fact that rejected recharge

returns to the streams as baseflow indicates that there are small local groundwater flow systems operating at the top of

the intake beds and that these local systems are highly connected to the surface water system. If this connectivity is

accepted then it is highly probable that any groundwater extraction in the intake beds that disrupts the water balance of

the local flow systems will also have an influence on the volume of rejected recharge that is returned to the rivers and

streams. That is, any storage deficit that occurs in the aquifer due to groundwater pumping will draw on water that would

have previously reported to streamflow. There would also be changes to the connectivity estimates if the initial recharge

rates to the intake beds are much higher than the quoted 0.5% rate allowing for the volume of recharge that is rejected.


Figure 5-1. Map showing Great Artesian Basin Intake Beds and Great Artesian Basin Jurassic aquifer system and losing and gaining

streams within the Darling River Basin


5.2 Groundwater use in Great Artesian Basin aquifers

Groundwater use from the GAB within the northern New South Wales and southern Queensland portion of the DRB is

divided into the following zones: Zone 1A, eastern recharge; Zone 1B, southern recharge; Zone 3, Warrego; and Zone 4,

central (GABCC, 1998). The current annual extraction limit for the recharge zones (zones 1A and 1B) is determined from

estimated recharge to the sub-areas minus that which is deemed necessary for maintaining groundwater-dependent

ecosystems (GDEs).

The four types of GAB systems adopted here are the GAB Intake Beds, GAB Alluvial, GAB Cap Rock and GAB Jurassic.

Data supplied by the New South Wales Department of Natural Resources for GAB use in the various zones are

summarised in the Appendix (Tables A1 to A4). Significant water volumes are drawn from the GAB in all but the cap rock

system; however, this varies from one river basin to another. Allocation is at, or higher than, the long-term average

extraction limit in the GAB Intake Beds within the Border Rivers and Macquarie regions, although current total usage is

considerably lower than entitlement. Current usage for the GAB Jurassic in the Barwon-Darling region is close to, or

higher than, the long-term average extraction limit. The GAB Alluvial is over-allocated in the Gwydir and Border Rivers

regions.

The draft water sharing plan for the New South Wales GAB groundwater sources (NSW Govt, 2007) has identified the

amounts of extraction that can satisfy the needs of the GDEs. For the eastern recharge area (Border Rivers region) this

is 13.3 GL/year and for the southern recharge area (upper reaches of Castlereagh, Macquarie and Bogan rivers) this is

29.7 GL/year. For the Surat (lower Macquarie and lower Castlereagh rivers) the current licences are 18.8 GL/year. The

values are 667 ML/year for Warrego and 161 ML/year for the central area. The current (as of 1999) usage is much higher

than the above allocations primarily due to free flowing extraction of about 102 GL/year primarily in the Surat and

Warrego zones.

In Queensland, the areas of interest are primarily the Surat and Warrego zones just north of the border with New South

Wales, and possibly the southern Barcaldine zone. Current extraction is about 29 GL/year from the Hooray sandstone

aquifer in the Surat zone. Extraction from the Barcaldine area is estimated to be about 10–20% of that from the Surat

zone and mostly from the Hutton sandstone aquifer.

Tables A1 to A4 in the appendix summarise data supplied by New South Wales on groundwater use and long-term

extraction limits for the four GAB GMUs.

5.3 Interactions with water sharing plans

For the surface water sharing plans, the agreed river model is calibrated over a given period of time and this calibration

requires incorporation of terms accounting for the losses to or gains from groundwater. Where losses or gains change

with time due to groundwater extraction, such changes need to be quantified and incorporated into the river models that

are being developed in this project and the Australian Hydrological Modelling Initiative (e.g., due to increases in pumping

or drawdown). These need to be explicitly accounted for where (i) extraction might impact on an extraction limit or

sustainable yield estimate of an overlying GMU, and (ii) where losses and gains can impact on GAB.

The Groundwater Management Plan sets limits that are less than the current pumping rates and as such will have an

effect on:

• potential for downward leakage

• upward leakage to baseflow via alluvial aquifers to streams

• upward leakage to watertable aquifer.

The influence of the GAB aquifers are explicitly accounted for in the river models for the Lower Macquarie (losses) and

Lower Namoi (gains). In the Lower Macquarie groundwater model there is 5.39 GL/year flowing to the north-west out of

the groundwater model in the GAB layers and this represents the annual average flow for the 1980 to 2003 calibration

period. There is also an estimated 2.49 GL/year inflow to the model in the GAB layers. The Lower Namoi has an

average of 8.3 GL/year inflow from the GAB. The GAB is not included in the Gwydir model because of the influence of

impermeable shales that impede upward discharge. For the GAB west of the Border Rivers, the relevant model assumes

baseflow is entirely from the GAB.


6 Key messages

The Great Artesian Basin (GAB) underlies a large portion of the Darling River Basin in northern New South Wales and

southern Queensland. The influence of the main J-aquifer is not considered explicitly in any of the groundwater modelling

undertaken for the project. However, the impacts of the estimates from the modelling results are explicitly accounted for

through leakage of water from river channels to the intake beds of the GAB.


Castlereagh region of New South Wales (Region 8), the Border Rivers region of New South Wales and Queensland

(Region 5), and the Condamine-Balonne region of Queensland (Region 3) where the regions traverse the intake beds of

the GAB in their middle reaches. Of lesser significance are the Warrego, Gwydir and Namoi regions (regions 2, 6 and 7).

The extent of impacts of current and proposed water extraction limits of the GAB water sharing plan on the current and

projected sustainability of the Darling River Basin surface water systems are known only approximately, but in general

are likely to reduce baseflow. More detailed work in those areas identified above is required to provide quantitative

estimates. Interventions such as the GAB bore rehabilitation program will likely have little impact on the Darling River

Basin systems in New South Wales due to the time lags by virtue of large distances between the artesian bores and the

intake beds and corresponding impacts on connectivity with surface water systems.


7 References

Abbott WE (1884) Water supply in the interior of NSW. J. Proc. Royal Soc. NSW, 18, 85-111.

Bierwirth PN and Welsh WD (2000) Delineation of recharge beds in the Great Artesian Basin using airborne gamma radiometrics and satellite remote sensing. Bureau Rural Sciences, Canberra.

Brownbill R (2000) NSW Great Artesian Basin Status Report. NSW Dept. of Land and Water Conservation, 37pp + 2 Appendices.

David TWE (1983) Artesian water in NSW and Qld. J Proc. Royal Soc. NSW. 27, 408-443.

DWR (1991) Water resources in the Castlereagh, Macquarie and Bogan valleys. Dept. Water Resources, NSW. Report.

Downes RG and Sleeman JR (1955) Soils of the Macquarie region, NSW. Soil Publ. No.4, CSIRO, Melbourne.

Dyce PH and Dowling TI (1997) Mapped biophysical themes produced for reconstructing historical salt balances and stream salinity trends in the catchments of the Murray-Darling basin. CSIRO Land and Water Tech. Rep. 19/97

Evans WR, Hillier J, and Woolley DR (1994) Hydrogeology of the Darling River Drainage basin: Qld/NSW, Australia. 1:1 000 000 Map Sheet, AGSO (Geoscience Australia), Canberra.

GABCC (Great Artesian Basin Consultative Council) (1998) Great Artesian Basin Resource Study. R. Cox and A. Barron, eds., 235p.

Habermehl MA (1980) The Great Artesian Basin, Australia. BMR Journal of Geology & Geophys. 5, 9-38.

Habermehl MA (1998) Hydrogeology and hydrochemistry of the Great Artesian Basin, Austalia. AGSO (Geoscience Australia) Canberra, ACT.

Habermehl MA and Lau JE (1997) Hydrogeology of the Great Artesian Basin, Austalia (map 1: 2 5000 000) AGSO (Geoscience Australia) Canberra, ACT.

Herczeg AL, Torgersen T, Chivas AR, and Habermehl MA (1991) Geochemistry of groundwater from the Great Artesian Basin, Australia. J. Hydrol. 126: 225-245, 1991.

Ife D and Skelt K (2004) Murray-Darling Basin Groundwater status 1990-2000. Summary report. MDBC, Canberra

Kellett JR, Ransley TR, Coram J, Jaycock J, Barcaly DF, McMahon, GA, Foster LM and Hillier JR (2003) Groundwater Recharge in the Great Artesian Basin Intake Beds, Queensland Department of Natural Resources and Mines Technical Report.

Keshwan M (1995) River loss investigation in the Macquarie River downstream of Narromine. Dept. Land and Water Conservation, Dubbo, NSW.

McKenzie NJ (1992) Soils of the Lower Macquarie Valley, NSW. CSIRO Div. Soils Rep. No. 117. CSIRO

Mulholland C St.J (1950) Review of southern intake beds, NSW and their bearing on on artesian problems. In: Geol. Surv. Geological Reports 1939-1945, Dept. of Mines, NSW p. 125-127.

NSW Govt. (2007) Water Sharing Plan for the Great Artesian Basin Groundwater Sources 2007. (Draft report).

Radke BM, Ferguson J, Cresswell RG, Ransley TR, Habermehl MA (2000) Hydrochemistry and implied hydrodynamics of the Cadna-owie – Hooray Aquifer, Great Artesian Basin. Bureau of Rural Sciences, Canberra ISBN 0 642 47554 7.

Sleeman JR, and Downes RG (1950) Part 1: Soil survey of proposed irrigation area – Narromine, NSW. Div. Soils rept. 3/50 CSIRO, Adelaide.

Taylor S (1994) Macquarie River catchment land management proposal for the integrated treatment and prevention of land degradation, Macquarie River catchment – Conservation and Land Management, NSW.

Wolfgang C (2000) Hydrogeology of the Pilliga Sandstone, Coonamble Embayment and Water Resource Management. PhD Thesis, Fenner School of Environment, The Australian National University.


8 Appendix

8.1 Data from the groundwater management units of the Great

Artesian Basin with reference to water allocation and current

use

Table A1. GMU GAB (Jurassic)

Zone Region Est. recharge

LTAEL Total entitlement

Unassigned water

% Allocated 2004/05 Usage (metered)

2004/05 Total use

ML/y ML

GAB - Central Barwon-Darling 1,054 1,334 -280 100% (Local Area Rules)

707 1,594

GAB - Central Paroo 262 207 55 78.9 152 317

GAB - Central -Residual (outside CSIRO MDB Catchments)

Nil 4,987 4,270 717 85.6 2 2,871

GAB - Warrego Zone Barwon-Darling 11,628 10,503 1,124 90.3 115 7,393

GAB - Warrego Zone Warrego 5,537 4,969 568 89.7 0 3,419

GAB - Warrego Zone Condamine-Balonne 750 995 -244 100% (Local Area Rules)

0 662

GAB - Surat Zone Condamine-Balonne 10,779 3,985 6,794 37.0 0 837

GAB - Surat Zone Barwon-Darling 30,210 18,796 11,414 62.2 665 8,457

GAB - Surat Zone Gwydir 9,811 20,065 -10,255 100% (Local Area Rules)

81 3,899

GAB - Surat Zone Namoi 2,158 977 1,181 45.3 0 663

GAB - Surat Zone Border Rivers 3,886 7,583 -3,698 100% (Local Area Rules)

4 887

GAB - Surat Zone Moonie 236 8 228 3.4 0 7

Table A2. GMU GAB (Alluvial)



Unassigned water

% Allocated

2004/05 Usage (metered)

2004/05 Total use

ML/y ML

Barwon-Darling_GAB Alluvial_NP-_Mod-

Barwon-Darling 152,894 5,761 147,133 3.8 0 4,599

Barwon-Darling_GAB Alluvial_NP-_Mod+

Barwon-Darling 0 0 0

Border Rivers_GAB Alluvial_NP-_Mod-

Border Rivers 23,922 1,583 22,339 6.6 0 1,136

Condamine-Balonne_GAB Alluvial_NP-_Mod-

Condamine-Balonne

53,671 792 52,879 1.5 0 520

Gwydir_GAB Alluvial_NP-_Mod-

Gwydir 43,008 3,790 39,218 8.8 107 2,600

Gwydir_GAB Alluvial_NP-_Mod+

Gwydir 0 0 0 0

Macquarie-Castlereagh_GAB Alluvial_NP-_Mod-

Macquarie-Castlereagh

64,242 12,057 52,185 18.8 351 8,027

Moonie_GAB Alluvial_NP-_Mod-

Moonie 1,209 3 1,206 0.2 0 2

Namoi_GAB Alluvial_NP-_Mod-

Namoi 9,919 394 9,525 4.0 0 331

Warrego_GAB Alluvial_NP-_Mod-

Warrego 1,250 18 1,232 1.4 0 14


Table A3. GMU GAB (Cap Rock)

Zone Region Estimated recharge


Unassigned water


2004/05 Total use

ML/y ML

Barwon-Darling_Great Artesian Basin_NP-_Mod-

Barwon-Darling

0.06 25,739 3,757 21,982 14.6 0 2,883

Condamine-Balonne_Great Artesian Basin_NP-_Mod-

Condamine-Balonne

0.06 1,384 113 1,271 8.2 0 90

Paroo_Great Artesian Basin_NP-_Mod-

Paroo 0.06 2,623 594 2,029 22.6 0 341

Warrego_Great Artesian Basin_NP-_Mod-

Warrego 0.06 9,145 964 8,181 10.5 0 731

Table A4. GMU GAB (Intake Beds)



Unassigned water


2004/05 Total use

ML/y ML

Border Rivers_Great Artesian Basin_NP-_Mod-

Border Rivers 0.06 9,284 31,895 -22,611 Over allocated 9,135 10,148

Gwydir_Great Artesian Basin_NP-_Mod-

Gwydir 0.06 4,016 2,585 1,431 64.4 1,266 1,853

Macquarie-Castlereagh_Great Artesian Basin_NP-_Mod-

Macquarie-Castlereagh

0.06 24,000 23,798 202 99.2 4,534 6,278

Namoi_Great Artesian Basin_NP-_Mod-

Namoi 0.06 4,062 3,848 214 94.7 347 833

Namoi_Great Artesian Basin_NP-_Mod+

Namoi 0 0 0 0

Barwon Darling Barwon-Darling 1,618 354 1,264 21.9 0 170


Background report on the Great Artesian Basin€¦ · Background report on the Great Artesian Basin A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable

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