Guillermo Umana Macquarie University ENVG267 Snowy River Environmental Flows Report 2012 Table of Contents 1. Introduction 2. Findings 2.1 . Natural and Current Total Flow Volumes 2.2 Seasonal Variability in Flows 2.3 Flood event Frequencies 3. Discussion 4. Recommendations 5. References Executive Summary It is clear now, after 10 years of environmental flows down Jindabyne dam, that the progress in regaining environmental stability in the Snowy River has been little. This report draws on previous monitoring reports from different sources, including the Snowy River Scientific Committee, The Snowy Water Inquiry and Snowy River Alliance, to compare the pre and post Hydroelectric Scheme environmental state of the Snowy River with its current state. It can be argued that the main 1
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Guillermo Umana
Macquarie University
ENVG267
Snowy River Environmental Flows Report 2012
Table of Contents
1. Introduction
2. Findings
2.1 . Natural and Current Total Flow Volumes
2.2 Seasonal Variability in Flows
2.3 Flood event Frequencies
3. Discussion
4. Recommendations
5. References
Executive Summary
It is clear now, after 10 years of environmental flows down Jindabyne dam, that the
progress in regaining environmental stability in the Snowy River has been little. This report
draws on previous monitoring reports from different sources, including the Snowy River
Scientific Committee, The Snowy Water Inquiry and Snowy River Alliance, to compare the
pre and post Hydroelectric Scheme environmental state of the Snowy River with its current
state. It can be argued that the main reasons for lack of environmental flow target-meeting
are droughts and the water entitlements payed by the government such as the Mowamba
Borrowing account. This report concludes that droughts and environmental variability will
continue as the effects of climate change become stronger in South-Western Australia, so
they should not be an excuse not to release adequate environmental flows into the Snowy
River. Political will should be enhanced by further transparency in the monitoring and
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increasing role of the now inactive Snowy Scientific Committee. The government should
repay all borrowings as soon as possible and make sure that future flows mimic seasonal
flows in a more adequate way. Today sedimentation continues to be a problem, as well as
invasive vegetation and poor habitat for native species. It is recommended that a new
Snowy Inquiry takes place to create new targets that better reflect the current situation of
the river and the effects of climate change.
1. Introduction
The Snowy Mountains Scheme diverts the water of 12 rivers and 71 creeks in the Snowy
Mountain region to generate hydro-electric power and provide water for irrigation of lands
to the West of the Snowy River (Smith, 2000). The economic and social importance of the
Scheme contrasts with the environmental degradation that diverting the waters generate.
Since the begging of the Scheme’s operations, 99% of the Snowy River’s natural flow below
Jindabyne Dam has been diverted, producing sedimentation, poor habitat quality for native
species and lack of water mixing among other problems (Smith, 2000).
Map 1. Illustrative Map of the Lake Jindabyne Area (Australian Geographic, 2011)
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In 1997 with the Snowy Hydro Corporation Act, the governments of New South Wales,
Victoria and the Commonwealth created the Snowy River Inquiry, a project to gather
community and expert opinions about the future of the Snowy River. The Inquiry provided
the government with a series of composite options to generate a positive impact on the
Snowy River. In 2002, a historic agreement between NSW, Victoria and the Commonwealth
was signed to return 21% of the Snowy’s natural flow by 2012 (ADE, 2010). This meant that
by 2012, more than 120 GL of water should have been flow down the Snowy (Snowy
Scientific Committee, 2008). In reality the flows did not surpass 38Gl a year between 2005
and 2009.
Map 1 (above) shows the Snowy River at Jindabyne Dam, which is the dam that was chosen
in 2002 to release the environmental flow. The map also shows the Mowamba River, which
provided the Snowy with environmental flows for a period of time from 2002 to 2005. These
flows had to be re-payed to Snowy Hydro Ltd by the government(s) through the Mowamba
Borrowing Account, which meant that after 2006, the environmental flows to the Snowy
were reduced to allocate the water to other Snowy Hydro commitments (ADE, 2010). This
reduction was also reinforced by the droughts that occurred during the first decade of the
21st century. Anyhow, La Niña events during 2010-2011 have meant that more water is
being allocated to the environmental flows in recent years.
This report argues that the environmental flow scheme should avoid being dependant on
climate change to deliver appropriate flows to the river. A review of the current procedures
should be made to adapt the flows to a less climate-dependant scheme. Also, monitoring
transparency and political will should be enhanced to make the environmental flows
become a regular activity, with constant improvements.
2. Findings
2.1 Natural and Current Total Flow Volumes
The Snowy Water Scheme requires that at least 2,088 GL of water are diverted to the
Murray and Murrumbidgee systems each year, from which more than half comes from the
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Snowy catchment (Smith, 2000). Table A provides information on natural and actual flows of
the Murray, Murrumbidgee and Snowy and the amount of households dependant on those
rivers.
Table A. Key Statistics for the three main Snowy River Scheme River (Smith, 2000: 9)
It is clear from the table that percentage of difference between the natural flow of the
Snowy and its current flow is much greater than the one for the other 2 rivers. Although
tributary rivers provide the Snowy with extra water below Jindabyne, the flow at its mouth
is half of what it would be at natural flow.
On the other hand the number of households benefited directly by the Murray and
Murrumbidgee is more than 6 times the one for the Snowy River. Smith (2000) points out
that the irrigated lands of the Murrumbidgee and Murray support agricultural production
over $750 million a year with water from the Scheme. The Scheme also produces 38% of
Australia’s hydroelectric power (Erskine, 1999A). The economic importance of the water
diversion is obvious, but the importance to recuperate the Snowy River is also evident. Both
interests can be met more accurately if Climate Change and transparency are enhanced, as
argued below.
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2.2 Seasonal variability in Flows
The reduction of flows in the Snowy River cannot be seen as a simple reduction of water
volume. The impact on native species, water variability, flow duration and frequency of
floods are some of the recorded effects of the 30 years of constant flows at 1% of the
natural levels (Erskine, 1999A). Figure 1 (below) shows a comparison of the flows of the
Snowy River below Jindabyne Dam and Dalgety. Both comparisons not only show a massive
reduction of flows but also a complete lack of seasonality, which is essential for the health
of native species, the movement of sediments downstream and water mixing. Degradation
of the river environment downstream of Jindabyne is in a great extent caused by the lack of
seasonality.
Figure 1. Changes in mean monthly discharge pre-and-post-SMHS (Erskine et al., 1991A: 9)
It can be argued that stronger peak flow events are needed. Although environmental flows
since 2002 have aimed to input seasonal variation, the effects have been minimal. Since
2010, peak flows have been increased in days and volume (as shown in the discussion
below) but furthering peak flows in spring are needed to fully clear the sedimentation
problems, especially at the mouth of the river and provide native species with regular
seasonal changes.
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2.3. Flood Event Frequencies
Figure 2. Pre-and post- Jindabyne Dam annual flow volumes at Dalgety (Rose & Bevitt,
2003: 14)
Figure 2 (above) shows the impact of the Scheme in flood variability and baseline flows in
the Snowy River. While the average flows prior to 1966 were above 1000000 ML a year, the
average flows from 1966 to 1995 were well below 200000 ML a year. Most importantly, the
variability of floods was very high prior to the scheme, with peak years reaching 25000000
ML. During the operation of the scheme, the Snowy has not seen annual flows above
500000 ML.
The environmental flows up to now have not been able to fully address the sedimentation
and poor river habitats generated by low flows. Even after the first environmental flows in
2002, the mouth of the river has been having entrance closures (see Picture 1). For example
on 31st of December 2006, the entrance closed, and was manually opened on 4th of March
2007, only to close again on the 9th of April (Wheeler et al, 2009). A factor that has made
environmental flows ineffective is a reduction of snow melting in the snowy mountains
because of less snow precipitation. Lower volumes from the tributaries of the Snowy mean
weaker discharges to the ocean. Floods with a peak discharge size at least four times greater
than the mean annual flood are important in mobilising sediment (Rose & bevitt, 2003). An
adjustment of the environmental flows is needed to address the impacts of less and less
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snow in the Snowy Mountains and less and less water from tributaries to support
environmental flows.
Picture 1. Google earth View of the end of the Snowy River