Shoalhaven Water Supply Transfers and Environmental Flows August 2006
Discussion Paper
ShoalhavenShoalhaven RiverRiver
WaterWater SupplySupply TransfersTransfers andand EnvironmentalEnvironmental FlowsFlows
SH001-08-06V1 Contents
What is this paper about? 1
What is the Government seeking to do? 4
SCA bulk water supply system for Sydney, Illawarra, Blue Mountains, Southern Highlands towns and Shoalhaven communities 8
What is the SCA’s Shoalhaven Water Supply Transfer Scheme? 10
Why is SCA’s Shoalhaven Water Supply Transfer Scheme important? 13
How healthy are the Shoalhaven and Southern Highlands rivers? 14
What have people said they value about Shoalhaven and Southern Highlands rivers? 20
How may Tallowa Dam operate in the future? 22
What would be the new environmental flows in the Shoalhaven River below Tallowa Dam? 24
Putting it all together: what interaction is possible between environmental flows below Tallowa Dam and dam operations? 31
Water transfers through the Southern Highlands 35
What will be the impacts of these options on the Southern Highlands rivers? 49
What are the next steps? 52
How can you be involved? 54
Glossary and acronyms 55
This document is copyright © Sydney Catchment Authority. Photographs on pages 18 and 25 supplied courtesy of the Department of Natural Resources. All other photography by TVU Pty Ltd © Sydney Catchment Authority. What is this paper about?
The New South Wales Government’s 2006 Metropolitan Water Plan secures the water supply for greater Sydney (including Illawarra and Blue Mountains) to 2015 and beyond.
One option in the plan is to transfer more water from the Shoalhaven River to greater Sydney communities while protecting the health of the Shoalhaven River. To do these two things, the Government is considering the impacts of water transfers on the Shoalhaven River, Lake Yarrunga (behind Tallowa Dam) and the rivers and streams in the Southern Highlands.
This discussion paper provides for community discussion on ways to:
• protect the health of the Shoalhaven River below Tallowa Dam by improved environmental flow release rules for the dam
• change the operation of Tallowa Dam to increase greater Sydney’s available water supply, without raising Tallowa Dam wall, while addressing the amenity of Lake Yarrunga
• reduce the impacts of using rivers as channels to transfer water through the Southern Highlands from Tallowa Dam to other Sydney Catchment Authority (SCA) dams.
All three elements are linked, and two – Shoalhaven River below Tallowa Dam and Tallowa Dam Operations – closely interact, as shown below.
Water supply Shoalhaven Tallowa Dam transfers through River below operations the Southern Tallowa Dam Highlands
Figure 1. Interaction between the three Shoalhaven water supply transfer and environmental flows elements
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
1 How can I have a say?
The NSW Government wants to hear what you have to say about the proposals. In making its decisions, the Government will consider community views and values, as well as technical and environmental assessments.
You can have your say in a variety of ways - at community information sessions, briefings, information displays - and you can provide your comments in any of the ways listed below. You can complete a ‘Have Your Say’ form or write your own submission. Provide your comments by:
Mail: Shoalhaven Community Consultation, Sydney Catchment Authority, PO Box 323, Penrith, NSW 2751
Phone: 1300 722 468
Fax: (02) 4721 0951
Email: [email protected]
Website: www.sca.nsw.gov.au
Hand in: At any of the displays and briefings.
Please send your comments by close of business Friday 6 October 2006.
What if I want to know more?
There are many ways to find out more about the proposals:
• Visit the SCA’s website www.sca.nsw.gov.au to access all available information. The website also has ‘Have Your Say’ forms to help you provide your feedback
• Ask for a CD with all the reports and supporting documents
• Visit the displays in Bowral, Nowra and Kangaroo Valley during the consultation period. The opening times and locations are:
Stockland Mall, Nowra Wednesday 10.00am to 5.30pm Thursday 1.00pm to 9.00pm
Oxley Mall, Bendooley Street, Bowral Friday 10.00am to 5.30pm Saturday 10.00am to 4.00pm
Kangaroo Valley Hall, Main Road, Kangaroo Valley Tuesdays 10.00am to 4.00pm
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
2 • Call in at one of the community information and feedback sessions:
Nowra School of Arts, 12 Berry Street, Nowra Thursday 14 September 2006 5:00pm - 9:00pm
Bowral CWA, Wingecarribee Street, Bowral Saturday, 16 September 2006 9.00am – 1.00pm
Kangaroo Valley Hall, Main Road Kangaroo Valley Saturday, 16 September 2006 2.00pm – 6.00pm
• Look out for newsletters and advertisements highlighting details of information sessions and other consultation opportunities
• Phone 1300 722 468 for more information about the consultation opportunities
• View the technical investigations, studies and reports at the display centres and community information and feedback sessions (see list of report names and numbers below).
Discussion Paper Shoalhaven Water Supply Transfers and Environmental Flows (SH001)
Shoalhaven environmental Tallowa Dam operation Southern Highlands water flows reports* reports supply transfer reports
• Shoalhaven Environmental • Aquatic Ecology Report • Shoalhaven Transfers Preliminary Flows Knowledge Review (SH018) Environmental Report (SH002) • Terrestrial Ecology Report (SH013) • Shoalhaven Environmental (SH017) • Geomorphology Report Flows Investigations • Geomorphology Report (SH014) (SH003) (SH016) • Aquatic Ecology Report • Cultural Heritage Assesment • Vegetation Report (SH012) Report (SH015) • Platypus Report (SH004) • Operations Options Report (SH011) • Fish Passage Report (SH019) • Cultural Heritage Report (SH005) (SH010) • Aquatic Invertebrates Report • Terrestrial Ecology Report (SH006) (SH009) • Physical Habitat Modelling • Tunnel Geotechnical Reports Report Vols 1,2 & 3 (SH007) (SH008)
* Other detailed technical studies are now under way and will be completed later in 2006
Figure 2. Report names and numbers
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
3 What is the Government seeking to do?
In the 2006 Metropolitan Water Plan the NSW Government gave the following undertakings:
• SCA would examine options for:
• operational changes to its existing Shoalhaven Water Supply Transfer Scheme to increase the long-term available water supply to greater Sydney by around 30 billion litres per year
• measures to mitigate the impacts of using rivers as conduits for the transfer of water
• to consult with the community about these options
• if Government does decide to transfer more water from Tallowa Dam, it will do so by protecting low flows in the Shoalhaven River downstream of the dam, and by only pumping a proportion of the medium and high flows.
Whether or not the Government decides to increase greater Sydney’s water supply by transferring more water from the Shoalhaven:
• Tallowa Dam wall will not be raised
• the health of the Shoalhaven River will be protected by implementing improved environmental flow release rules for Tallowa Dam
• future town water supply for Kangaroo Valley and Shoalhaven communities is secure
• water supply to Southern Highlands towns is secure
• Tallowa Dam will be drawn down by no more than three metres below full supply level
• Tallowa Dam will be modified to allow two-way fish passage over the dam wall, and to improve the quality of water released for environmental flows
• SCA will upgrade visitor facilities at Bendeela Camping Ground and Tallowa Picnic Ground
• SCA funding for sewage treatment plant upgrades, including new plants at Bundanoon and Kangaroo Valley, will continue
• catchment health programs will continue through the SCA’s Healthy Catchments Program, and programs delivered by the Hawkesbury Nepean and Southern Rivers catchment management authorities.
All SCA water supply and catchment health activities, current and proposed, are funded through its bulk water charges to Sydney Water Corporation (SWC) and its other customers. In the 2005-06 year, sales to SWC comprised 99.2 percent of the SCA’s total revenue from water sales.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
4 Tallowa Dam, which forms Lake Yarrunga, in on the junction of the Shoalhaven and Kangaroo rivers
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
5 2006 Metropolitan Water Plan
The 2006 Metropolitan Water Plan builds on the significant developments since the first plan was released in 2004. The 2006 plan, which was underpinned by advice from independent experts, contains a diverse range of rainfall and non-rainfall dependent measures. The combination of measures will meet greater Sydney’s water supply growth and security needs into the future. The plan responds to future changes in the demand and supply balance by using an adaptive management approach. It also provides a readiness strategy to deal with severe drought. The main elements of the 2006 plan are: Reducing the demand for water The residential sector accounts for some 70 percent of the drinking water used in Sydney. In contrast, the industrial sector uses 12 percent and the commercial sector uses 10 percent. There has been a significant reduction in water use per head, from 506 litres per day in 1991 to 403 litres per day today. Demand reduction measures in place and planned are projected to deliver additional savings of around 145 billion litres of water annually by 2015. Increasing recycling Currently greater Sydney recycles 15 billion litres per year. This is planned to increase to 70 billion litres a year by 2015. Actions include the Western Sydney Recycled Water Initiative - which includes substituting flow releases into the river from Warragamba Dam with highly treated recycled water - recycling for industry, a new sewer mining policy, making it easier to use greywater at home, and recycling stormwater. Increasing supply The focus has shifted from building new dams as was done in the past to making the best use of the existing water supply system. The major projects involve accessing deep water stored in Warragamba and Nepean dams. In addition potential operational changes to the Shoalhaven Water Transfer Scheme could increase water supply availability by around 30 billion litres per year. Managing Drought Reliance on rain-fed supplies makes Sydney vulnerable to drought. Measures such as accessing deep storage, water conservation and water recycling will make a significant contribution to a sustainable, long-term water supply for Sydney and add additional drought protection. However, they are not sufficient on their own to guarantee supply in the face of severe or extreme drought.
Groundwater and desalination of seawater are new lines of defence in severe drought. Borefield development to tap groundwater will begin if storage levels fall below around 40 percent. Building a desalination plant will begin if storage levels ever drop below about 30 percent. Money and time already invested in investigations and designs will reduce the lead time to build these options if we need them. Protecting catchment and river health The health of the rivers and their surrounding catchments is important to ensure supplies of high quality drinking water, to maintain dependent ecosystems, and to support the communities and economies that rely on them. The plan commits to providing environmental flows to rivers supplying water to Sydney and other communities. Understanding climate change Climate change adds to the uncertainty about future rainfall patterns. Climate change could mean longer and more intense droughts, but it could also mean more intense rainfall events in the catchments. The NSW Government, together with the CSIRO, the University of NSW, the University of Newcastle and the Australian Greenhouse Office, is examining how climate change may impact on water availability.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
6 The above mix of supply and demand measures is sufficient to meet Sydney’s growth needs to 2015 and to secure drought needs to 2015 and beyond.
#The total volume recycled is anticipated to be more than 70 billion litres every year by 2015. However, the use of recycled water for some purposes does not save drinking water. The total amount of drinking water expected to be saved through recycling is 59 billion litres per year.
*By investing in being ready to access groundwater and desalinated seawater in severe and extreme drought – even if such drought does not occur – more water can now be drawn from the dams without affecting the security of supply; for this reason the calculated water availability figure has increased even without accessing these sources.
^In a severe drought, new bore fields would be constructed to enable access to around 30 billion litres of groundwater a year for about three years for drought needs.
Figure 3. Meeting Sydney’s water needs to 2015 (from 2006 MWP)
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
7 SCA bulk water supply system for Sydney, Illawarra, Blue Mountains, Southern Highlands towns and Shoalhaven communities
Greater Sydney (metropolitan Sydney, the Illawarra and the Blue Mountains), Shoalhaven communities, including Nowra and Kangaroo Valley, and towns in the Southern Highlands all rely on capturing the runoff from rainfall and storing it in SCA dams. Rainfall in these areas is highly variable. This variability can result in low river flows for several years at a time.
Over the last 120 years, the greater Sydney region has had three severe droughts: in the 1890s, the 1930-40s, and the current drought. This is why the SCA stores more water per head of population than many other regions.
The SCA’s largest dam, Warragamba Dam (completed in 1960), stores 2,053 billion litres of water. It has the largest catchment but is furthest inland and is susceptible to drought. The catchments of the smaller dams of the upper Nepean, Woronora, Blue Mountains, and Shoalhaven River are less susceptible to drought.
Combined, the SCA’s 15 dams store up to 2,600 billion litres of water. Greater Sydney uses approximately 600 billion litres per year in a non-drought year. This amount has reduced to around 520 billion litres in each of the last two years, primarily due to the community’s response to water restrictions.
Figure 4. Map of existing water supply system for greater Sydney
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
8 Figure 5. Sydney, Blue Mountains, Illawarra and Nowra Water Supply System
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
9 What is the SCA’s Shoalhaven Water Supply Transfer Scheme?
How does the scheme work now?
Tallowa Dam stores water from the Shoalhaven and Kangaroo rivers in Lake Yarrunga for:
• transfer across the Southern Highlands to the SCA’s dams serving greater Sydney region’s water supply during drought
• release from the dam to supply the Shoalhaven community’s water supply
• hydroelectricity generation by Eraring Energy, and
• environmental flow releases down the lower Shoalhaven River.
Figure 5 shows how the scheme fits into the region’s water supply system.
When the scheme is operating, water is transferred from Tallowa Dam by three pump stations through a series of tunnels, pipelines and canals via Fitzroy Falls Reservoir, to Wingecarribee Reservoir.
From there, water is transferred down the Glenquarry and Doudles Folly creeks and the Nepean River to Nepean and Avon dams; and down the Wingecarribee and Wollondilly rivers to Warragamba Dam.
Water from the upper Nepean dams is then transferred down a short section of river to Pheasants Nest Weir, then through tunnels and the Upper Canal to Prospect Reservoir for Sydney’s water supply.
Kangaroo Valley is supplied with water from Bendeela Pondage near Tallowa Dam.
Bowral is supplied from Wingecarribee Reservoir.
The Illawarra area is supplied from the upper levels of Lake Avon.
Recreation is permitted on Lake Yarrunga and Fitzroy Falls Reservoir, unlike other SCA drinking water storages. This supports local tourism.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
10 Figure 6. Shoalhaven Water Supply Transfer Scheme
Figure 7. Annual inflows to Tallowa Dam and transfers to Sydney
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
11 Water is transfered from Fitzroy Falls Reservoir to Wingecarribee Reservoir via canal and tunnel
12 Why is SCA’s Shoalhaven Water Supply Transfer Scheme important?
The SCA’s Shoalhaven scheme makes an important contribution to the water supply system of the greater Sydney region, operating as a drought reserve scheme.
The scheme also provides water to Shoalhaven Water, which serves Shoalhaven communities. Wingecarribee Reservoir, within the scheme, provides water to the Wingecarribee Shire Council for Bowral, Mittagong, Moss Vale and surrounds.
Pumping from the scheme has happened three times since it began operating in 1977, from:
• 1981 to 1983
• 1993 to 1994
• 2003 to the present.
The total volume of water pumped to the greater Sydney system from 1977 to June 2006 was 990 billion litres. This is less than four percent of the total inflows into Tallowa Dam during that period. However, since 2003, in the current drought, around 48 percent of total inflows to the dam have been transferred (see Figure 7). From April 2003 to June 2006 the scheme supplied around 410 billion litres of water, or approximately 25 percent of the greater Sydney’s system demand under current restrictions.
The scheme makes an essential contribution to the annual long-term available water supply for greater Sydney. The SCA is able to draw more from Warragamba and its other dams because, if needed, it can call on water from Tallowa Dam’s storage.
The Government recognises that the historical way of operating the scheme has some negative impacts.
• Using the scheme as a drought reserve supply can stress the Shoalhaven River in times of extended low river flow.
• The scheme’s use of Southern Highlands’ rivers to transfer water to Sydney has had some adverse impacts on river and stream health.
• Some local people are also concerned about the impacts of variable water levels in Lake Yarrunga due to pumping from Tallowa Dam.
Since 1995 the Government has been seeking to lessen the impacts of dams on rivers, and of using NSW creeks and rivers to transfer water from dams.
The proposals in this discussion paper respond to all these concerns.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
13 How healthy are the Shoalhaven and Southern Highlands rivers?
Why is a healthy river important?
In Australia, as throughout the world, few rivers remain in pristine condition. Rivers have been modified to provide for important uses, such as drinking water supplies, irrigation for food and fibre production, generating electricity, and for recreation.
Meeting these needs means that rivers no longer function as completely natural systems. This can affect the survival of native plants and animals that depend on a natural river flow pattern.
For the purposes of this discussion paper, a healthy river is defined as one that has river flows and water quality that restore or mimic natural conditions to maintain:
• natural river processes
• diverse native plants and animals that depend on the long-term natural flow and water quality conditions
• diverse river habitats, for example riffles, pools and wetted banks, which are important to many plants and animals, and
• community uses.
How can healthier rivers be achieved?
In the 1990s, governments - including the NSW Government - realised the value of making specific river flow releases from dams to protect and improve river health. These environmental flows provide separate releases of dam water just for the health of the river.
Environmental flows maintain or restore conditions suitable for the breeding of native fish and other river wildlife, provide more diverse animal habitats, improve the health of in-stream and river-bank vegetation, and provide more variable river conditions which discourage pest species.
The total amount of water available to the environment from a dam is made up of active and passive environmental water.
• Active environmental water – is the water deliberately released as environmental flows from the dam. It provides the minimum amount of water to be released from a dam to the environment downstream. Rules for releasing dam water specify the way the flow is managed.
• Passive environmental water – is additional water to the active water released as environmental flows. It is the water that naturally spills over the dam when the dam is full. Passive environmental water remains after extractions for purposes such as drinking water supplies, irrigation, and environmental flow releases.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
14 For best effect, envirionmental flows need to operate within an integrated catchment management system. Providing better environmental flows can only partly ensure a healthy river if other river health aspects are not managed adequately.
Improved river water quality can be achieved through:
• managing the catchments, such as riverbank protection
• preventing pollutants entering the river, and
• providing environmental flows.
Some dams can only release deep water that is cold and low in oxygen. The quality of this dam water, when released as environmental flows, can be improved by mixing surface and deep waters, but when practical, the best solution is to release surface water.
Shoalhaven River upstream of Tallowa Dam
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
15 What about the Shoalhaven River system?
Upstream of Tallowa Dam
Tallowa Dam creates Lake Yarrunga which covers an area of 8.6 square kilometres. It is fed by two main rivers, the Shoalhaven River and the Kangaroo River, as well as by a number of smaller creeks and streams. The catchment for Tallowa Dam covers an area of 5,750 square kilometres. It is the second largest of greater Sydney’s drinking water catchments. (See catchment map inside back cover.)
Total inflows to Tallowa Dam vary significantly year to year (see Figure 7). Using rainfall records dating back to 1900, long-term average inflows have been calculated at approximately 1,040 billion litres per year.
The 250 kilometre Shoalhaven River and its tributaries provide approximately two-thirds of Lake Yarrunga’s water. The catchment’s soils are relatively infertile and land use is a mixture of grazing land and forest. Braidwood is the largest town in the catchment.
Clearing of riparian vegetation and widespread erosion contribute to poorer quality water entering the river and lake from this catchment. Nutrients and metals from the upper reaches flow down the river, with elevated levels of these contaminants entering the river during wet weather. Ecosystem health of the Shoalhaven River however, as estimated by measuring macroinvertebrates in the river over the last five years, is generally good.
Figure 8. Shoalhaven River showing fresh water and tidal-influenced estuary sections
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
16 The Kangaroo River and its tributaries provide approximately one-third of the lake’s water. It receives higher rainfalls and has better soils than the Shoalhaven River catchment. Grazing, cropping and dairy farming are the dominant land uses. The township of Kangaroo Valley is the most concentrated urban area. Intensive land use and wastewater runoff contribute high levels of nutrients and other contaminants to the river and lake. Notwithstanding, the ecosystem of the Kangaroo River is generally healthy in terms of supporting aquatic flora and fauna.
Water quality in Lake Yarrunga declines in wet weather, with high inflows of nutrients, metals and other contaminants. Nutrients, especially during summer, can give rise to high algae growth. This can cause occasional algal blooms and incidents of toxic blue-green algae in the dam. These occur more often in the Kangaroo River arm of the lake.
The draw down on the lake for water supply exposes parts of the river and lake bed and creates a ‘tidemark’ within the operating zone between the full storage level and the minimum operating level.
The lake supports many fish. It has well vegetated banks although weeds can prevail in the tidemark area. Some sediment has accumulated in the lake but this has not substantially affected the dam’s storage volume. The SCA, Southern Rivers Catchment Management Authority and Shoalhaven City Council are working together in major programs to address these issues.
The draw down on Lake Yarrunga creates a ‘tidemark’ between the full storage level and the minimum operating level of minus three metres
Downstream of Tallowa Dam
The Shoalhaven River downstream from Tallowa Dam to the ocean comprises:
• a freshwater section (about 27 kilometres) between Tallowa Dam and Burrier Weir, and
• a tidal-influenced estuary section (about 50 kilometres) between Burrier Weir and the Pacific Ocean.
The freshwater section consists of a narrow winding river valley that remains significantly unchanged from natural conditions. Much of the valley in this reach is protected in Morton National Park.
The river itself is relatively healthy, being close to its natural condition, and supporting a range of aquatic habitats such as shoals, riffles and rapids. Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
17 Factors affecting the health of this section include:
• the physical barrier of Tallowa Dam, and
• current operations for water supply transfers and environmental flow releases.
The dam is a barrier to fish that migrate between salt and fresh water such as the Australian Bass.
The current Shoalhaven scheme transfers water from Tallowa Dam during drought in greater Sydney. These transfers coincide with low river flows in the Shoalhaven River during drought and increases stress on the river at these times. The water transfers, however, have had little impact on moderate and high river flows in the lower Shoalhaven River. Since the current transfers began in April 2003, the dam has spilled on 10 occasions.
Historically, Tallowa Dam has released cold deep water downstream from the dam. This has had a negative impact on water quality. The SCA recently installed an aeration system in the dam to mix warmer surface and cooler deep water, which has improved downstream water quality.
Shoalhaven Estuary
The Shoalhaven River estuary is dominated by the tides with occasional freshwater flushes from the upstream river. These are important for estuarine health. The estuary is a valuable oyster growing area and recreational waterway. It also provides important waterbird and fish breeding habitats.
The estuary has been highly modified. The current opening to the ocean is at Crookhaven Heads. The entrance used to be further north at Shoalhaven Heads. However, in 1822 the European settler Alexander Berry cut a channel - Berrys Canal - through to the Crookhaven River. Tidal flows and successive floods have deepened and widened the channel, and it is now the main river channel. Berrys Canal has significantly altered the water flow of the lower estuary.
Like other NSW rivers, the estuary has also been affected in recent years by severe drought, mainly by altering the mix of salt and fresh water.
Shoalhaven Water Supply Berrys Canal (right) was built in 1822 - the Shoalhaven River now enters the ocean Transfers and Environmental Flows at Crookhaven Heads Discussion Paper - August 2006
18 What about Southern Highlands rivers?
The Southern Highlands rivers used for water transfers - Wingecarribee, Wollondilly and upper Nepean river systems - experience unnatural flow patterns when run-of-river transfers occur. The transfers mean that in times of drought, the rivers flow at higher than normal rates.
Much of the land surrounding the Wingecarribee River is substantially modified, especially in the high plain section of the Wingecarribee River from Wingecarribee Reservoir to Berrima where grazing is the dominant land use. These parts of the river provide poorer quality aquatic habitat, with evidence of poor ecosystem health and presence of pests. There are pockets of high quality environment such as Cecil Hoskins Nature Reserve. Downstream of Berrima the river habitat improves markedly. This river section also offers good to excellent habitat for platypus. This high quality environment continues into the dramatic Wollondilly River gorge.
Land surrounding Doudles Folly and Glenquarry creeks on the upper Nepean river system is used predominantly for grazing. These stream sections offer limited aquatic habitat and there is evidence of poor ecosystem health. Further downstream, the land is densely forested with high quality and diverse aquatic habitat with good ecosystem health. Platypus are seen more regularly in the upper Nepean River than in the Wingecarribee River.
What is being done to make these rivers healthier?
Improved river flows and large-scale catchment health programs by the SCA and Hawkesbury-Nepean, Southern Rivers and Metropolitan catchment management authorities (CMAs) are improving water quality. These complement and build on council and landholder activities.
The SCA is also:
• improving the quality of water released from Tallowa Dam
• limiting the transfer flow down the Wingecarribee and Nepean rivers, and Glenquarry and Doudles Folly creeks
• managing the quality of transfer water to control the spread of blue-green algae, and
• implementing the Wingecarribee Swamp and Special Area Plan of Management.
The SCA will also be building upstream and downstream fish passage ways at Tallowa Dam.
The Government is further protecting the lands surrounding the upper Nepean rivers by declaring them state reserves. Other steps to improve river flows include modifying Nepean River weirs.
The Metropolitan Water Plan has catchment and river health as part of its central focus. Most prominently, the plan commits to introducing scientifically based environmental flow releases from all SCA dams.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
19 What have people said they value about Shoalhaven and Southern Highlands rivers?
Previous public inquiries, such as the Healthy Rivers Commission’s 1999 Independent Inquiry into the Shoalhaven River System, provide some insight into the community’s values for these rivers and catchments.
More recently, SCA and DNR have asked local people to identify those aspects of the rivers’ physical, social, cultural and economic identity that are important to them. A Shoalhaven Community Reference Group has been meeting regularly with SCA and DNR to provide input and feedback on the development of the proposals detailed in this discussion paper.
A series of community values workshops were held in June 2006 in the Shoalhaven and Southern Highlands. The workshops:
• provided input into this discussion paper about the value of the Shoalhaven, Kangaroo and Southern Highlands rivers and their environs to their communities
• informed and tested the scope and direction of the proposals presented in this discussion paper to take account of the breadth of local community views
• identified the particular values of local communities
• provided opportunities to verify existing and capture new information, particularly from the Southern Highlands, on the importance and use of the rivers by the local communities for planned social and economic impact assessments.
What do local communities say they value most?
The outcomes of the early SCA and DNR consultations and values workshops gave the following information.
Shoalhaven River below Tallowa Dam
People living around the lower Shoalhaven have indicated that a naturally flowing river downstream of Tallowa Dam is a core value.
Other values centred on the functional uses of the river, in particular the quality and quantity of water available for uses such as major industry, agriculture and aquaculture.
People also indicated the need for equity between different local river users. This requires balancing human needs and the natural environment, and recognising the associated costs and benefits.
It was also considered important to understand potential conflicts between uses. River uses that are important to some people may have a negative impact on others, for example, cattle grazing on riverbanks can impact on water quality and aquaculture.
The overarching sentiment was that a healthy Shoalhaven River is a source of Shoalhaven Water Supply Transfers and Environmental Flows local pride. Discussion Paper - August 2006
20 Tallowa Dam and Kangaroo Valley
People in the Kangaroo Valley indicated that tourism was a major economic activity for the Kangaroo Valley / Tallowa Dam area. Maintaining the scenic, recreational and environmental qualities of Tallowa Dam and its environs was therefore a primary consideration. The local community valued stable water levels in the lake.
Fishing groups placed a high value on establishing fish passage past the dam and improving the quality of downstream water releases.
Recreation on Lake Yarrunga is highly valued by local communities
Southern Highlands
People from the Southern Highlands have indicated that water transfers have had a major impact on the environmental health of the local river systems.
The next most common values people identified were:
• protecting the area’s biodiversity and ecological integrity
• natural variable flows are essential for river health
• water is a resource to be valued, protected, and managed equitably
• property values should be protected.
The communities in the Southern Highlands strongly valued the ‘Wingecarribee River as the lifeblood of the Highlands’.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
21 How may Tallowa Dam operate in the future?
The future operation of Tallowa Dam to increase the long-term available water supply to greater Sydney by around 30 billion litres per year requires altering the current operating arrangements.
The main operating arrangements - the timing and volume of water supply transfers from Tallowa Dam - are determined by:
• the combined level of all SCA’s dams, expressed as a percentage of their full storage capacity (pump mark)
• the dam’s minimum operating level, which is how many metres below its full storage level that the dam is allowed to fall before transfers stops.
Pumping only occurs when the total SCA water storages are below the pump mark and the level of water behind Tallowa Dam is above its minimum operating level. When water in the dam reaches the minimum operating level, pumping from the dam stops.
To allow for the release of new environmental flows of the quantity and quality required, the SCA will need to upgrade the offtake structures of the dam wall. The final design of the new infrastructure will be determined once the new envirionmental flow rules are finalised.
How could Tallowa Dam operate to increase greater Sydney’s long-term available water supply by around 30 billion litres per year?
Transfers from Tallowa Dam currently begin when the level of all SCA’s dams falls below 60 percent full during prolonged droughts. Pumping stops when the dams rise above 65 percent full. Pumping only occurs in those conditions if the level of Tallowa Dam is above its minimum operating level.
Increasing the pump mark and varying Tallowa Dam’s minimum operating level would:
• provide the water to add the extra 30 billion litres to greater Sydney’s long-term available water supply, and
• provide the water needed for the new environmental flow rules from Tallowa Dam (discussed below).
Raising the pump mark means that water transfers could take place in wetter periods and higher flows. By doing this, Tallowa Dam would move from being a drought water supply to a fully integrated part of greater Sydney’s water supply system. This is a more effective way to harvest water and will generally take water from the Shoalhaven River when the river downstream of Tallowa Dam is less stressed.
Maintaining the Shoalhaven scheme’s existing water supply contribution to greater Sydney while also providing for future environmental flows outlined
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
22 below would require the pump mark to be raised above 70 percent. The possible range for the new pump mark would be 80 to 90 percent of the SCA’s total dam storage capacity.
The Government has limited the minimum operating level to the current three metres below full storage level.
The SCA is looking at different ways to operate the dam within a range from full storage level to three metres below full storage level to achieve the 30 billion litres of extra water and to provide for future environmental flows.
When full, Tallowa Dam has a total storage capacity of 90 billion litres. Operating with a minimum operating level of three metres below full storage means Tallowa Dam has an operating storage capacity of 22 billion litres. Reducing the minimum operating level to one metre below full supply level would minimise the impact of transfers on the amenity of the lake by reducing the tidemark and providing better recreational access. However, this would also reduce the operating capacity of the dam to less than eight billion litres.
Maintaining the minimum operating level at one metre below full storage means the pump mark would need to be a little higher (one to two percent) and the period for transfers a little longer than when operating at minus three metres.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
23 What would be the new environmental flows in the Shoalhaven River below Tallowa Dam?
As discussed earlier, environmental flow rules for the Shoalhaven River downstream of Tallowa Dam are needed because of the impact of the dam, its effect on river flows, and the use of the river for water supply purposes.
The approach taken to determine the environmental flow requirements for the Shoalhaven River below Tallowa Dam involves assessing the water needs of the river’s complete ecosystem, including its main river channel, river banks, estuary and important ecological features, such as rare and endangered species.
If the essential features of a river’s natural flow can be identified and adequately incorporated into environmental flow rules, its natural functioning and its flora and fauna are likely to be maintained or restored.
Applying this approach to the lower Shoalhaven River involves the following steps:
1. Knowledge review Reviewing past studies of the environmental water needs of the river (Shoalhaven Environmental Flows Knowledge Review - see Figure 2).
2. Investigations a. Identifying and analysing natural flow patterns that would have existed before Tallowa Dam and water supply transfers from the dam began (using hydrological (flow) computer models)
b. Assessing the current river flows downstream
c. Identifying what aspects of river flow are critical for protecting or restoring river health using the NSW River Flow Objectives Framework
d. Establishing two environmental flow active rule sets that indicate the range of possible releases from Tallowa Dam that both mimic the Shoalhaven River’s natural river flows (identified in step 2a) and provide the required 30 billion litres of increase in the long-term available water supply (using computer models)
e. Undertaking detailed environmental studies on the river, for example on water quality fish passage and flora and fauna
f. Independently assessing the social and economic impacts of the two active rule sets.
(Shoalhaven Environmental Flows Investigations - see Figure 2)
3. Values and uses assessment Consulting with the community on what they value about the Shoalhaven River and how they use the river.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
24 4. Recommended environmental flow rules Recommend the final preferred set of environmental flow rules to Government based on:
• the environmental studies (step 2e)
• community values and uses (step 3), and
• social and economic studies (which stem from community comment) on the two indicative active environmental flow rule sets (see below).
This discussion paper deals with steps 1 to 3.
Reports providing more information are available with this discussion paper and are detailed in Figure 3. The independent economic and social assessment (step 2f) and other detailed technical studies now under way will be completed later in 2006. They will provide input into step 4.
Step 4 will be completed over October - November 2006. DNR will recommend the new active environmental flow rule set to Government by the end of this year.
The rule set will then be included in the draft Water Sharing Plan for the Greater Metropolitan Region which will be released for public comment next year.
How can the essential features of natural river flow patterns be identified?
The NSW river flow objectives (RFOs) provide the framework to identify the key elements of river flows that are important for protecting river health and maintaining community uses. The framework has provided the basis for establishing environmental flows for rivers and streams across NSW.
The RFOs identify 12 aspects of natural river flow that protect or restore river health and provide the river environment needed for human uses such as recreation and aquaculture. They are the high-level goals for managing flows in rivers, streams and other types of surface water.
Table 1 sets out all 12 objectives and highlights the eight priority objectives for the Shoalhaven River downstream of Tallowa Dam and how these may be addressed.
Shoalhaven Water Supply Shoalhaven River freshwater riffles downstream of Tallowa Dam Transfers and Environmental Flows Discussion Paper - August 2006
25 Table 1. River flow objectives for the Shoalhaven River system
River flow Aspects of river flow critical to Relevance of RFO to the Shoalhaven River below Tallowa objectives protect or restore river health Dam
RFO 1* Protect natural water levels in Will be met by the upcoming Metropolitan Water Sharing river pools and wetlands during Plan which will provide the means to ensure that pools periods of no flow are protected. Additionally, there is limited extraction in the freshwater reach RFO 2 Protect natural low flows Priority for developing Shoalhaven environmental flow rule – discussed further below RFO 3 Protect or restore a portion of Protecting a portion of moderate flows and freshes is a freshes and high flows priority for developing environmental flow rules. High flows will continue to occur as spill events – discussed further below RFO 4 Maintain wetland and floodplain Will be considered but not a priority for developing the inundation Shoalhaven environmental flow rules as the focus of this objective is structures on floodplains that prevent inundation of flood plains and wetlands. Big flow events required to inundate the wetlands and floodplains below Tallowa Dam will be unaffected by proposals to transfer extra water from the Shoalhaven to greater Sydney RFO 5 Mimic the natural frequency, The Shoalhaven River is a permanent stream, and not a duration and seasonal nature of naturally temporary waterway drying periods in naturally temporary streams RFO 6 Maintain or mimic natural flow Priority for developing Shoalhaven environmental flow variability in all rivers rules - discussed further below RFO 7 Maintain natural rates of change in Objective will be achieved through rules set to achieve water levels RFO 6 RFO 8 Manage groundwater for Managed through Macro Water Sharing Plans for ecosystems groundwater currently being developed RFO 9 Minimise the impact of in-stream Already actioned: modifications to Tallowa Dam will structures improve fish passage and quality of water released RFO 10 Minimise effects of dams on Already actioned: modifications to Tallowa Dam will water quality. provide better water quality releases. RFO 11 Ensure that the management of Already actioned: a priority for Shoalhaven environmental river flows provides the flow rules. Continued capacity to provide flows to meet necessary means to address contingencies will remain part of the operation of Tallowa contingent environmental and Dam. DNR will continue to determine when such dam water quality events releases are to be made RFO 12 Maintain for rehabilitate estuarinn Priority for developing Shoalhaven environmental flow processes and habitats rule
* RFOs highlighted in bold type are priority objectives for the Shoalhaven River downstream of Tallowa Dam
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
26 How are the priority river flow objectives for the lower Shoalhaven being addressed?
Three river flow objectives for the lower Shoalhaven are already being addressed: one (RFO 1) in the drafting of the Metropolitan Water Sharing Plan and two (RFOs 9 and 10) through modifications to Tallowa Dam. The five remaining flow objectives (RFOs 2, 3, 6, 11 and 12) are discussed below.
Meeting the five remaining river flow objectives requires establishing new environmental flow rules for the SCA to release water from Tallowa Dam. These rules provide the active environmental water discussed earlier in this paper.
Determining environmental flow rules
Determining environmental rules depends on understanding that the lower Shoalhaven River, like all rivers, has varying types of river flow classes. These are made up of:
• low flows
• moderate flows
• freshes (substantial rises in the river for short periods after a rainfall event)
• high flows.
To understand and then mimic the natural river patterns, each river flow class is broken down into five flow aspects:
• flow magnitude – volume of the varying flows
• flow duration – length of time for which the flows occur
• flow frequency – how often the flow event happens
• flow variability – natural systems depend on variability inflow rates
• seasonality of flows – seasonal variation in flow events.
Each class and aspect of river flow supports different physical and ecological functions.
DNR’s analysis and modelling looked at all these river flow aspects for each river flow class and how they would be expected to change as a result of the possible future environmental flow rule for Tallowa Dam.
DNR and SCA then prepared a shortlist of two active environmental flow rule sets that can potentially meet both water supply and river health needs (see Table 2).
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
27 The following sections discuss the five critical river flow objectives and how they would be managed.
RFO 2 – Protecting natural low flows
Low flows are small volume flows that happen regularly. They are important to maintain river ecosystems particularly in prolonged dry periods. Protecting low flows in the lower Shoalhaven River requires releasing water from Tallowa Dam based on the dam’s inflows.
The current (interim) environmental flow rule requires that inflows to the dam of up to 90 million litres per day (ML/day) must effectively be passed straight through the dam. Fixed volumes of water additional to the environmental flow are also released for Shoalhaven City Council’s extraction at Burrier. The current environmental flow rule provides some natural flow variability for the downstream river when inflows to the dam are between zero and 90 ML/day. However when inflows exceed 90 ML/day, the dam contributes no additional water to river flow variability downstream.
DNR’s hydrological modelling shows that is possible to provide the required water supply and increase the low flow rule at Tallowa Dam from 90 ML/day to somewhere in the range of 150 to 250 ML/day. A low flow rule within this range would better protect natural low flows downstream of Tallowa Dam and improve their variability. Parts of the river could then better sustain plants and animals in drier periods. For example, more variable low flow over riffles (river shoals and rapids) would provide improved habitat for small fish, macroinvertebrates and other small aquatic animals.
RFO 3 – Protect or restore a portion of moderate flows, freshes and high flows
Moderate flows and freshes are important to help maintain the river channel and riparian (river-bank) vegetation. They also trigger fish breeding and increase the release and distribution of food supplies. High flows are floods that will continue to spill over the dam. They are important for rejuvenating rivers and estuaries.
To achieve the objective of protecting or restoring a portion of moderate flows and freshes, a proportion of all incoming flows in addition to the volume allocated for the low flows (ie 150 to 250 ML/day) would be released from the dam.
Hydrological computer modelling shows that dam releases of up to 30 percent of Tallowa Dam inflows in the moderate to high range are achievable, while still delivering the long-term available water supply of 30 billion litres per year.
The 30 percent proportion of inflows would pass through the dam as variable volume flows, and would contribute to flow variability in the Shoalhaven River downstream. Downstream tributaries that enter the river below Tallowa Dam would boost this flow.
High flows will continue to spill over the dam even when the SCA is pumping.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
28 RFO 6 – Maintaining or mimicking natural flow variability
Natural flow patterns are important to sustain native river-dependent plants and animals that have adapted to variable river flow conditions. The environmental flow rules for release of water from Tallowa Dam will (combined with naturally occurring spills) reflect the natural pattern of its inflows.
RFO 11 – Contingent flows
Contingent flows are additional flows released from the dam for specific ecological or riverine purposes.
Tallowa Dam will continue to have the capacity to provide such flow releases to meet contingencies. DNR, as the regulator, will continue determining when such dam releases are to be made as set out in SCA’s water management licence.
RFO 12 – Maintain or rehabilitate estuarine processes and habitats
The proposed environmental flow rules above will help maintain the Shoalhaven River’s key estuary processes. Because of its importance, DNR is undertaking additional investigations beyond the hydrological analysis and modelling. These estuary investigations include further examining potential Tallowa Dam flow rules and estuary salinity levels. The findings of these investigations will provide input into final recommendations to Government.
What would the environmental flows rules be for Tallowa Dam?
To increase greater Sydney’s long-term available water supply by 30 billion litres per year, DNR and SCA modelling and hydrological analysis shows that there are two indicative active environmental flow rule sets. These are set out in Table 2.
The difference between the two active environmental flow rule sets is that Rule Set 1 allocates more water to the medium flows or freshes and Rule Set 2 allocates more water to the low flows.
Both rule sets provide the bases for assessing how the rivers flora and fauna and the important social, economic and cultural values can be maintained.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
29 Table 2. River flow objectives (RFOs) under different environmental flow rules
Environmental RFO 2 RFO 3 RFO 6 RFO 11 RFO 12 flow rules Protect Protect or restore Maintain or mimic Contingent flows Maintain or natural low of a portion of natural flow rehabilitate flows moderate flows, variability estuarine freshes and high processes and flows habitats
Current Rule 100 % Not protected 100% of inflows Continued capacity to Currently no protection of above 90 ML/day only up to 90 ML/ provide flows to meet protection of flows up to day then only after contingencies will freshes 90 ML*/day dam spills remain part of the operation of Tallowa Dam Active 100 % Protect 30% of 100% of inflows Continued capacity to Objective will be Environmental protection of incoming flows up to 150 ML/day provide flows to meet achieved Flow Rule flows up to above 150 ML/day contingencies will through rules set Set 1 150 ML/day plus 30% of remain part of the to achieve RFO inflows above 150 operation of Tallowa 6 and possibly ML/day Dam RFO 11 Active 100 % Protect 20% of 100% of inflows Continued capacity to Objective will be environmental protection of incoming flows up to 250 ML/day provide flows to meet achieved Flow Rule flows up to above 250 ML/day contingencies will through rules set Set 2 250 ML/day plus 20% of remain part of the to achieve RFO inflows above 250 operation of Tallowa 6 and possibly ML/day Dam RFO 11
*ML = Megalitre, or one million litres
Total environmental water
The above rules address the provision of active environmental water. For those periods of time when Tallowa Dam is at or above full supply level and significant inflows occur, river flows would pass over the dam wall as passive environmental water.
The total percentage of Tallowa Dam inflows available for total environmental water (active and passive) would range from 92 to 94 percent on average, and between 86 and 89 percent in dry periods.
Ecological processes
As noted previously, the next step is to assess how key ecological processes are likely to respond to the narrowed range of rules for the dam operation and environmental flows presented in this paper (step 2e).
Further scientific studies will provide better understanding of river flow / ecology relationships. Feedback from this discussion paper will help inform how the key social, economic and cultural heritage values associated with the Shoalhaven River downstream of Tallowa Dam can be best addressed by the
Shoalhaven Water Supply new environmental flow rule set (step 2f and 3). Transfers and Environmental Flows Discussion Paper - August 2006
30 Putting it all together: what interaction is possible between environmental flows below Tallowa Dam and dam operations?
As the diagram below illustrates, new environmental flow releases from Tallowa Dam and new dam operating arrangements interact.
Environmental flows (active and passive) Amount and timing of water releases from Tallowa Dam
Trade-offs between water availability and environmental impacts Sydney dams total Minimum operating storage level level (MOL) Levels when water transfers Level in Tallowa Dam at start and stop which pumping stop (pump mark)
Figure 9. Balance between water availability and environmental impacts
The answer to each of the following questions affects the response to the others:
• What new environmental flow rule set should be adopted for Tallowa Dam?
• What is the best pump mark to use?
• What should be the minimum operating level of Tallowa Dam?
Table 3 shows possible combinations of these factors based on the two active environmental flow rule sets from Tallowa Dam that would provide the 30 billion litres per year increase in long-term available water supply. Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
31 32 Table 3. Impacts of various environmental flows and dam operational arrangements Active environmental flow Operating arrangements for Tallowa Dam Impacts of environmental flow rules from Tallowa Dam rule sets for releases from water supply transfers and proposed operating arrangements Tallowa Dam to the lower Shoalhaven River Pump mark Pump mark and Impact on Tallowa Dam (Lake Impacts on downstream Impacts on volume pumped (Percentage of the SCA’s minimum dam Yarrunga) Shoalhaven River from Shoalhaven River total system storage level) operating level to to start transfers stop transfers
Present When SCA’s total system When SCA’s total Over the long-term, water Impact is concentrated Over the long-term, an storage falls below 60% full system storage rises supply transfers occur during low flow/drought average of approximately All Tallowa Dam inflows up above 65% full 10 - 15% of the time periods 12 - 15 billion litres of water to 90 ML/day are released is transferred per year if the from the dam down the OR Water levels in Tallowa Dam Flow protection and current flow rule and lower Shoalhaven River vary significantly during these variability are only operating arrangements When Tallowa dam transfer periods provided for very low were to continue falls to three metres flows below full supply level Capacity to provide flows to meet contingencies
Active Environmental Flow At the point when SCA’s When SCA’s total Water transfers could Mimics natural river flow Over the long-term, if Flow Rule Set 1 total system storage falls system storage rises potentially occur: variability to a much Rule Set 1 and related below: above the nominated greater degree than at operating arrangements were • All Tallowa Dam inflows pump mark • 20 - 25% of the time to present implemented, an average of up to 150 ML/day • 70 - 75% to maintain (likely to be 80-85%) maintain the current approximately: released from the dam the Shoalhaven Shoalhaven contribution Low river flows down the lower scheme’s current OR to long-term water protected (but less than • 20 - 25 GL/year would Shoalhaven River contribution to long- supply availability Rule Set 2) be transferred to term water supply When Tallowa Dam maintain the current • 30% of inflows above availability of 75 GL*/ falls to its nominated • 35 - 40% of the time for There would be less Shoalhaven contribution 150 ML/day released year minimum operating Shoalhaven to contribute moderate flows and to long-term water form the dam down level - which would an additional 30 GL/year freshes compared to the supply availability the lower Shoalhaven • 80 - 85% full for be in the range of to long-term water present flow rule but River Shoalhaven to -1 to - 3 metres supply availability this Rule Set provides • 45 - 55 GL/year would contribute the below full storage more protection for be transferred for additional 30 GL/year level Water levels in Tallowa Dam medium flows and Shoalhaven to contribute to long-term water would vary significantly within freshes than Rule Set 2 an additional 30 GL/year supply availability the set operating range to long-term water during these transfer periods Capacity to provide flows supply availability to meet contingencies *GL = Gigalitre, or one billion litres Active environmental flow Operating arrangements for Tallowa Dam Impacts of environmental flow rules from Tallowa Dam rule sets for releases from water supply transfers and proposed operating arrangements Tallowa Dam to the lower Shoalhaven River Pump mark Pump mark and Impact on Tallowa Dam Impacts on downstream Impacts on volume pumped (Percentage of the SCA’s minimum dam (Lake Yarrunga) Shoalhaven River from Shoalhaven River total system storage level) operating level to to start transfers stop transfers
Active Environmental Flow At the point when SCA’s When SCA’s total Over the long-term, water Mimics natural river flow Over the long-term, if Rule Rule Set 2 total system storage falls system storage rises transfers could potentially variability to a greater Set 2 and related operating below: above the nominated occur degree than at present arrangements were • All Tallowa Dam pump mark implemented, an average of inflows up to All low flows protected • 70 - 75% to maintain (likely to be 80-85%) • 20 - 25% of the time to approximately: 250 ML/day would be the Shoalhaven maintain the current released from the dam More reduced moderate scheme’s current OR Shoalhaven contribution river flows and freshes • 20 - 25 GL/year would down the lower contribution to long - to long-term water be transferred to Shoalhaven River When Tallowa Dam compared to the present term water supply supply availability flow rule and Rule Set 1 maintain the current availability of 75 GL/ falls to its nominated Shoalhaven contribution • 20% of inflows above minimum operating • 30 - 35% of the time for year Capacity to provide river to long-term water 250 ML/day would be level - which would Shoalhaven to contribute flows to meet supply availability released from the dam • 80 - 85% full for be in the range of an additional 30 GL/year contingencies down the lower Shoalhaven to -1 to - 3 metres to long-term water • 40 - 50 GL/year would Shoalhaven River contribute the below full storage supply availability be transferred for additional 30 GL/year level Shoalhaven to contribute to long-term water Water levels in Tallowa Dam an additional 30 GL/year supply availability would vary significantly within to long-term water the set operating range supply availability during these transfer periods 33 Operational arrangements – next steps
SCA expects it could refine operational arrangements to achieve the 30 billion litres additional long-term water supply availability while reducing the volume pumped from the Shoalhaven River shown above. This would limit the increase in pumping costs, potentially reduce variability in Tallowa Dam water levels, and further reduce the downstream impact of Tallowa Dam. It could also provide flexibility to respond to future uncertainties in climate, supply and demand.
Feedback from this discussion paper will help inform how the key social, economic and cultural heritage values associated with Tallowa Dam can be best addressed by the new operational arrangements.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
34 Water transfers through the Southern Highlands
What are the impacts of the current water transfers through the Southern Highlands?
The 2006 Metropolitan Water Plan recognises the need to develop and discuss options that will mitigate the impacts of using Southern Highlands rivers to transfer Shoalhaven water.
The impacts can be summarised as:
• Alteration of natural river flows - the existing Shoalhaven transfers reduce river flows in the Shoalhaven River and increase the river flows in some Southern Highlands rivers and streams
• Local access difficulties - at several locations localised flooding causes physical access problems for landowners
• Local erosion - particularly when combined with cattle grazing on river banks
• Potential transfer of animals and plants from one system to another - there is a risk that transferred plants and animals may out-compete local populations, decrease their variety, and reduce their ability to cope with environmental change.
Transfers have occurred only in drought when the total volume of water stored in the SCA dams fell to trigger levels. This has occurred on three occasions since the1970s, each period lasting several years. During the current drought, water transfers began when storage levels fell to around 60 percent in April 2003 and have continued longer than on previous occasions. Water transfers will continue until dam levels recover, which could occur in a matter of weeks should a significant rain event occur over the Warragamba catchment (on average a rain event of this type occurs every 10 years), or it might take some years - the last significant event being in 1998.
The flow rates in the river channels are limited to minimise the impact on the river ecology, to reduce erosion, and to minimise localised flooding. The existing flow rate limits are 600 ML/day between mid-March and mid- September, 400 ML/day between mid-September and mid-March, and 200 ML/day for transfers commencing between November and January.
Any impacts related to the transfer of animals and plants between river systems are likely to have already occurred as the transfers have taken place over many years.
Any options discussed below that involve ongoing use of rivers to transfer water will result in a continuation of these impacts. The degree of impact would depend on flow rates and duration of transfers.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
35 What are the options for transferring water in the future?
The SCA has undertaken preliminary studies to identify a shortlist of six water supply transfer options. The option analysis has included the constraints, broad costs, advantages and disadvantages of each option. This shortlist was developed as a result of considering more than 100 possible options.
The shortlist has been developed from initial considerations of:
• achieving the increased 30 billion litres per year long-term available water supply
• technical feasibility
• construction and operational environmental impacts
• community, social and economic impacts, and
• capital and operating costs.
Investigations were done in enough detail for the main impacts of the options to be understood. More detailed environmental assessments would be needed before the Government can make any decision on a preferred option.
Where new pipelines were envisaged it was considered that above ground pipelines would be unacceptable on amenity and environmental grounds. Consequently underground pipeline options have been developed based on the maximum economically feasible pipe diameter of 1.8 metres.
Refinement of the options will be based on engineering, environmental, social and economic assessments and feedback from this discussion paper.
The six transfer options are outlined below. Discussion of each option focuses on the key features, social and environmental issues, and mitigation measures. The options have not been subjected to a detailed cost estimate at this stage. Early estimates are that the costs would range from tens of millions to three to four hundred million dollars. A comparative order of costs is indicated in the following pages using a ‘ ’ symbol.
The routes of the six options are shown on the map in Figure 10.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
36 Figure 10. Transfer options in the Southern Highlands
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
37 What are the advantages and disadvantages of each option?
Option 1
Increased run-of-river water transfers
Option 1 involves extending run-of-river transfers down the Wingecarribee and Wollondilly rivers to Warragamba Dam, and down Glenquarry and Doudles Folly creeks into the upper Nepean River then to Nepean Dam. Transfers would be limited to the existing flow rate but would occur for longer periods than at present.
Why this option?
This option does not involve building any new pipelines or tunnels, but increases the duration of water transfers through the Southern Highlands
Environmental and social issues
Option 1 would increase the current impact on affected creeks and rivers by approximately tripling the long-term average volume and duration of water transferred. Transfers would also occur during wetter periods which would increase impacts on the river environment and cause more local flooding.
More frequent use of these creeks and rivers for transfers of longer durations would further reduce periods of natural variability in these streams. For example, the river systems could have flows of between 400 to 600 megalitres a day (ML/day) in times when there should be a natural low flow, or no flow at all.
Prolonged artificial flooding of the flat upper reaches of the Wingecarribbee River would occur for longer periods. This would result in loss of use of farmland and create temporary difficulties with owners’ access to their land.
Transfers would continue to cause localised scouring and erosion where banks have been disturbed, especially in the 25 kilometre length of streams in cleared grazing areas. Downstream of these grazing lands, the streams are protected from substantial erosion by the existing natural bedrock and cobble armouring of riverbed and bank. The transfers would have limited impacts on the overall shape of the Wingecarribee and Wollondilly rivers and Glenquarry and Doudles Folly creeks.
There would be longer-term impacts on plant and animal habitats as a result of prolonged flows. Wetland areas would be flooded for longer periods with the potential for long-term damage. Animals can be flushed away and habitats modified making recolonisation difficult. Plant and animal pests such as carp are favoured by constant flows. Longer duration flows may also have a long- term impact on platypus by reducing banks available for burrows and riparian vegetation for shelter, and making it harder to feed in the fast flowing rivers.
There would be minimal additional impacts on terrestrial environments or cultural heritage items because there would be no increase in the flow rates.
No hydropower energy recovery is possible with this option.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
38 Mitigation
Limited measures could be adopted to reduce but not eliminate some of the impacts of run-of-river transfers. However, significant long-term impacts on existing rivers would remain.
Improved river management would be needed to prevent local erosion and to help manage the impacts of adjoining land uses. Encouraging plantings in riverbank areas and the exclusion of cattle would provide more diverse riparian habitats along the rivers.
For land affected by flooding, measures could include localised riverbank stabilisation and improved access points, but these may further reduce natural stream conditions.
There is no opportunity within this option to offset greenhouse gas emission generated by additional pumping.
Cost =
Under Option 1 water transfers would continue via the Wingecarribee River
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
39 Option 2
Upper Wingecarribee River bypass pipeline
Option 2 involves building a 1.8 metre diameter, 11 kilometre long underground pipeline from Wingecarribee Reservoir to Berrima Weir.
The pipeline would enable flow transfers of up to 500 ML/day to bypass this upper section of the Wingecarribee River. There would be no transfers in this section of river. The Wingecarribee and Wollondilly rivers downstream of Berrima Weir (approximately 120 kilometres) would have a transfer flow of up to 500 ML/ day for longer durations than at present.
There would continue to be run-of-river flows down Glenquarry and Doudles Folly creeks and the upper Nepean River to Nepean Dam but at a lower flow rate (200 ML/day) than at present.
Why this option?
Option 2 eliminates flows along the Wingecarribee River from Wingecarribee Reservoir to Berrima Weir thus reducing the length of stream affected. Reduced flow rates to Nepean Dam would reduce the impact on this system.
Environmental and social issues
There would be some increased impact compared to current transfer operations due to the longer duration flows in the Wingecarribee River for a length of approximately 40 kilometres downstream of Berrima Weir. This would affect the high quality aquatic environment, including platypus populations, until the junction with the much larger Wollondilly River. From this point to Warragamba Dam the impact of transfer flows would be reduced by the influence of natural flows from the Wollondilly River.
Pipeline construction would temporarily disturb predominantly grazing areas near the Wingecarribee River. The route would require two pipeline crossings of the Wingecarribee River that could potentially destabilise wetland areas, riverbanks and channels. An easement would need to be retained over privately-owned land above the pipeline.
Lower flows in the Nepean River would improve the current situation. With the river flow remaining within the riverbanks and adjacent flood plains there would be minimal additional impacts on terrestrial environments or cultural heritage items.
No hydropower energy recovery is possible for this option.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
40 Mitigation
Measures could be adopted to reduce but not eliminate some of the impacts of construction and of the residual run-of-river transfers.
Pipeline construction could be managed to reduce the potential for damage or removal of vegetation and heritage items if they occur along the route. Similarly, design and construction of stream crossings could be managed to minimise impact.
Removal of transfers from the Wingecarribee River to Berrima Weir would provide opportunities to re-establish a diversity of riparian habitats along this 20 kilometre length of river. It would also require new environmental flow releases from Wingecarribee Reservoir to better mimic natural river flows in this length of river.
Downstream of Berrima Weir, improved river management would be needed to rectify local erosion and to help manage the impacts of adjoining land uses.
There is no opportunity within this option to offset greenhouse gas emission generated by additional pumping.
Cost =
Option 3a
Upper Nepean tributaries bypass short pipeline
Option 3a involves building a 1.8 metre diameter underground pipeline, up to 4.2 kilometres from Glenquarry Cut (near Wingecarribee Reservoir) to the Nepean River downstream of its junction with Doudles Folly Creek.
This pipeline would bypass Glenquarry and Doudles Folly creeks. It would increase the duration of transfers in the upper Nepean River and the transfer flow rate would increase from 600 ML/day to up to 700 ML/day. This flow rate is substantially above the natural base flow and is above existing transfer rates. Run-of-river transfers down the Wingecarribee and Wollondilly rivers could be reduced to a maximum of 200 ML/day.
The pipeline route would go through grazing land, along roads and through a two kilometre section of undisturbed forest in the SCA’s catchment area.
Why this option?
Option 3a removes transfers from the smaller Glenquarry and Doudles Folly creeks but continues to impact other rivers already affected by transfers. It increases the maximum transfer flow in the Nepean River.
Environmental and social issues
Increased transfers would be concentrated in the bedrock dominated gorge of the Nepean River. The high quality aquatic environment of this 20 kilometre length of the Nepean River would be impacted by the increased flows. In particular there is likely to be significant impact on general habitat quality. Animals could be flushed away and habitat modified by the higher flows.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
41 Platypus burrows could be flooded, young platypus drowned and the availability of food altered. There would be limited impacts on the overall shape of the stream as a result of transfers.
This option would eliminate local transfer impacts in Glenquarry and Doudles Folly creeks upstream of the discharge point.
The lower flow rate along the Wingecarribee River would see a reduction in local flooding, reduced erosion impacts and improved habitat for platypus.
Pipeline construction would follow disturbed areas for 2.2 kilometres of its length and through undisturbed forest for approximately two kilometres in the SCA’s catchment area. This would require the creation of a pipeline construction and access corridor typically around 20 to 25 metres wide through forest that includes an endangered ecological community. Pipeline crossings of streams have the potential to destabilise banks and channels.
This area is also generally weed free and clearing for a pipeline corridor may encourage weed growth.
Potential Aboriginal cultural heritage sites are more likely to occur within this undisturbed area.
Some hydropower energy recovery is possible with this option.
Mitigation
Measures could be adopted to reduce but not eliminate some of the impacts of construction and the run-of-river transfers.
Careful assessment would be needed of any significant plant communities, habitat or heritage sites that may be identified along the route so the pipeline could be diverted or built to minimise impacts. Pipeline crossings of streams would require careful construction to prevent destabilising banks and channels.
Improved management would be needed along the Wingecarribbee River to address ongoing local erosion and to help manage the impacts of adjoining land uses.
Removal of transfers from the Glenquarry and Doudles Folly creeks would provide opportunities to re-establish a diversity of riparian habitats along these lengths.
This option provides a limited opportunity for energy recovery within the system by the introduction of hydropower generation.
Cost =
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
42 Option 3b
Upper Nepean tributaries bypass long pipeline
Option 3b is a variant of Option 3a and involves building a 1.8 metre diameter underground pipeline, 7.7 kilometres from Glenquarry Cut to the Nepean River below McGuires Crossing to release water further downstream than option 3a.
Transfer durations and flow rates would be similar to those in Option 3a.
The pipeline route would go through grazing land, partially disturbed areas adjoining roads, and through a four kilometre section of undisturbed forest within the SCA’s catchment area.
Why this option?
Option 3b removes transfers from the Glenquarry and Doudles Folly creeks and part of the upper reaches of the Nepean River. It continues to impact other rivers already affected by transfers and increases the maximum transfer flow in the Nepean River.
Environmental and social issues
Impacts on creeks and rivers would be similar to option 3a with the benefit of removing transfers from a section of the upper Nepean River by increasing the length of pipeline carrying transferred water.
Pipeline construction would follow disturbed areas for approximately 3.7 kilometres and through undisturbed forest in the SCA’s catchment area for approximately four kilometres. This would require building a pipeline construction and access corridor through forest that includes an endangered ecological community. Potential Aboriginal cultural heritage sites are more likely to occur within this undisturbed area.
The lower flow rate along the Wingecarribee River would see a reduction in local flooding, reduced erosion impacts, and improved habitat for platypus.
Some hydropower energy recovery is possible with this option.
Mitigation
Measures could be adopted to reduce but not eliminate some of the impacts of construction and the run-of-river transfers.
Careful selection and assessment of potential routes would be needed to identify significant plant community, habitat or heritage sites that may be along the pipeline route. The pipeline would need to be diverted to avoid them or built in ways to minimise impacts.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
43 Pipeline crossings of creeks or streams would need to be carefully managed to prevent destabilising banks and channels.
This option results in the removal of transfers from Glenquarry and Doudles Folly creeks, part of the upper reaches of the upper Nepean River, and the partial removal of transfers from the Wingecarribee River. It provides opportunities to re-establish a diversity of riparian habitats along these lengths of river.
Compared with Option 3a, this option could provide some additional potential to recover energy within the system by the introduction of hydropower generation.
Cost =
Options 3a and 3b would see a new underground pipeline built to transfer water from Glenquarry Cut (pictured) to the upper Nepean River
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
44 Option 4
Wingecarribee Reservoir to Lake Avon pipeline
Option 4 involves building a 1.8 metre diameter, 22 kilometre long underground pipeline from Glenquarry Cut to Avon Dam to carry 700 ML/day.
The pipeline route would go through grazing and cleared land, adjoining roads, and would travel through a two kilometre section of undisturbed forest near Avon Dam. It would require building an access road to the Lake Avon discharge point.
A 200 ML/ day run-of-river transfer would still be needed down the Wingecarribee and Wollondilly rivers.
Why this option?
This option would eliminate run-of-river transfers down Glenquarry and Doudles Folly creeks and the Nepean River, and reduce transfer rates in the Wingecarribee and Wollondilly rivers.
Environmental and social issues
Option 4 would substantially reduce the overall impact of transfers on Southern Highlands rivers and streams.
Stopping transfers to the Nepean Dam would remove the adverse impacts of transfers on the high quality aquatic habitats and platypus populations of the streams flowing to the dam. Aquatic habitats could return to natural condition and quality within SCA land.
There would be increased impacts on land from construction of the pipeline on a 10 kilometre stretch of the partially disturbed but good quality forest areas adjoining Tourist Road and catchment fire trails, and approximately two kilometres of undisturbed forest in the SCA’s catchment area. A cleared corridor approximately 20 to 25 metres wide would be required.
The route affects an endangered and valuable ecological woodland community, sensitive swamp environments, and includes a number of creek crossings.
Potential Aboriginal cultural heritage sites may occur within the undisturbed and partially cleared areas.
The lower flow rate along the Wingecarribee River would see a reduction in local flooding, reduced erosion impacts, and improved habitat for platypus.
Significant hydropower energy recovery is possible - up to 18 megawatts or around 30 percent of the energy used for transfer pumping.
Mitigation
Measures could be adopted to reduce but not eliminate some of the impacts of construction and the remaining run-of-river transfers down the Wingecarribee River.
Careful assessment would be needed of any significant plant community, Shoalhaven Water Supply habitat or heritage sites identified along the route so the pipeline could be Transfers and Environmental Flows Discussion Paper - August 2006
45 diverted to avoid them or built to minimise impacts.
Pipeline crossings of streams would require careful construction to prevent destabilising banks and channels.
This option would provide opportunities to re-establish a diversity of riparian habitats along rivers currently used to transfer water.
This option would also offer the opportunity for significant energy recovery within the system through hydropower generation.
Cost =
Option 5
Burrawang to Lake Avon tunnel
Option 5 involves building a three metre diameter, 20 kilometre long tunnel from Burrawang Pumping Station to Avon Dam.
This is the minimum economically viable tunnel diameter and has a capacity of up to 1,500 ML/day. Under this option the water transfer rate through the tunnel would be between 900 and 1,500 ML/day. The average volume of water transfered per year under Option 5 would be similar to Options 1 to 4.
The tunnel would generally be between 50 and 150 metres below ground in the southern section and 20 to 50 metres deep in the northern section. In the northern section it would generally follow the line of an existing power easement.
There would be entry, exit and midway access points to construct the tunnel, and a new access road to the discharge point at Avon Dam.
Why this option?
Option 5 has the lowest environmental impact and provides the most environmental benefits.
It would remove the need for any run-of-river transfers through the Southern Highlands, has much lower impact on land than pipelines, and bypasses Wingecarribee Reservoir. It provides the most operational flexibility. It does not involve pumping from Fitzroy Falls to Wingecarribee Reservoir thus saving energy and greenhouse gas emissions.
Environmental and social issues
Option 5 removes transfers from all creeks and rivers, allowing them to return to close to natural flows and condition. With appropriate environmental releases from Wingecarribee Dam to the Wingecarribee River, natural variability could be returned to both river systems with resulting benefits to natural aquatic diversity.
This option would eliminate local erosion and flooding that may have been caused by transfers.
Shoalhaven Water Supply Bypassing Wingecarribee Dam would improve the SCA’s capacity to manage Transfers and Environmental Flows water quality. Discussion Paper - August 2006
46 There would be some construction impacts at access points to the tunnel, spoil disposal areas, and for approximately two kilometres of undisturbed forest at the Avon Dam end of the tunnel.
Potential Aboriginal cultural heritage sites may occur within this undisturbed area or where the tunnel access points are located.
There is a potential to recover up to 50 megawatts of hydropower - or equivalent to around 60 percent of energy used for transfer pumping. Because the tunnel would provide gravity flow to Lake Avon, pumping required from Burrawang Pump Station would virtually be eliminated.
Mitigation
Rehabilitation measures could be adopted to reduce the construction impacts of this option.
If significant habitat or heritage sites are identified near access points or other surface elements, the tunnel could be designed to avoid them.
Implementing this option would result in the removal of all run-of-river transfers thus providing opportunities to re-establish a diversity of riparian habitats.
This option offers the opportunity for substantial energy recovery within the system through hydropower generation.
Cost =
When passing through SCA protected catchment, Options 4 and 5 would generally Shoalhaven Water Supply Transfers and Environmental Flows follow the line of an existing power easement Discussion Paper - August 2006
47 Option 6
Illawarra Spur pipeline
Option 6 is only possible in conjunction with Options 4 and 5 which transfer water to Avon Dam.
It involves building a 0.9 metre diameter, eight kilometre long underground pipeline connecting Option 4 or Option 5 to the existing water supply pipeline into the Illawarra water treatment plant.
The pipeline generally follows fire trails and crosses some forest areas within the protected catchment area.
Why this option?
It would improve water supply security to the Illawarra and provide additional long-term available water supply to greater Sydney through freeing up 67 billion litres of water in deep storage in Lake Avon.
Environmental and social issues
There would be impacts on land from the construction of the pipeline.
There would be short-term impacts from building the pipeline on aquatic environments at creek crossings. There would also be impacts on the areas of undisturbed forest along the route and the potential for impact on cultural heritage sites within this undisturbed area.
Some hydropower energy recovery is possible.
Mitigation
Measures could be adopted to reduce the construction impacts of this option. The smaller diameter pipeline would allow techniques such as directional drilling in some areas.
Implementing this option involves pipeline crossings of streams that would require careful construction.
Careful assessment would be needed of any significant plant community, habitat or heritage sites along the route so the pipeline could be diverted to avoid them or built to mitigate impacts
Cost =
Options below Nepean and Avon Dams
Options 3a, 3b, 4 and 5 involve transferring more water to Nepean Dam or Avon Dam and would mean some additional transfers of water along the rivers downstream of these dams. The SCA is examining the impacts of different options for conveying this additional water to Prospect Reservoir.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
48 What will be the impacts of these options on the Southern Highlands rivers?
To evaluate these options against the Government’s aim of mitigating impact on Southern Highlands rivers, SCA has reviewed the options against the NSW river flows objectives for the upper Nepean River system and the Wingecarribee and Wollondilly system.
Table 4 sets out the 12 river flow objectives and discusses how the objectives relevant to the Southern Highlands rivers would be addressed by the various options – listing the options from those that best meet each objective, to those that are less successful at meeting each objective.
Table 4. How river flow objectives are addressed by the transfer options
River flow Aspects of river flow Ability of options to address objectives critical for protection or relevant objectives restoration of river Relevance of the objectives to water health transfers along Southern Highland rivers
RFO 1 Protect natural water Option 5 achieves this objective. levels in river pools and Option 4 achieves this objective in wetlands during periods the upper Nepean system only of no flow Options 2, 3a and 3b partially achieve this objective by removing transfers from sections of rivers Option 1 does not meet this objective Run-of-river transfers remove most no-flow periods RFO 2 Protect natural low flows Option 5 achieves this objective Option 4 achieves this objective in the upper Nepean system only Options 2, 3a and 3b partially achieve this objective by removing transfers from sections of rivers Option 1 does not meet this objective Run-of-river transfers remove most low flows
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
49 River flow Aspects of river flow Ability of options to address objectives critical for protection or relevant objectives restoration of river Relevance of the objectives to water health transfers along Southern Highland rivers
RFO 3 Protect or restore a Option 5 achieves this objective portion of freshes Option 4 achieves this objective in and high flows the upper Nepean system only Options 2, 3a and 3b partially achieve this objective by removing transfers from sections of rivers Option 1 does not meet this objective Run-of-river transfers remove this ‘pulsing’ of flows, which includes freshes. Moderate flows are also affected. The highest flows are generally unaffected RFO 4 Maintain wetland and Option 5, and to a lesser extent floodplain inundation Option 4, achieves this objective Options 1, 2, 3a and 3b may increase inundation Run-of-river transfers can lead to increased inundation when supplemented by high natural inflows RFO 5 Mimic the natural Options 3a, 3b, 4 and 5 achieve this frequency, duration objective and seasonal nature Options 1 and 2 do not meet this of drying periods in objective naturally temporary streams Run-of-river transfers have reduced drying periods in smaller streams RFO 6 Maintain or mimic Option 5 achieves this objective natural flow variability Option 4 achieves this objective in in all rivers the upper Nepean system only Options 2, 3a and 3b partially achieve this objective by removing transfers from sections of rivers Option 1 does not meet this objective Run-of-river transfers generally remove variability
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
50 RFO 7 Maintain natural rates of Option 5 achieves this objective change in water levels Option 4 achieves this objective in the upper Nepean system Options 2, 3a and 3b partially achieve this objective by removing transfers from sections of rivers Option 1 does not meet this objective Run-of-river transfers remove natural rates of change but are managed to ensure stream levels do not rise or drop too quickly RFO 8 Manage groundwater All options achieve the objective for ecosystems Run-of-river transfers do not deplete groundwater RFO 9 Minimise the impact of Options 4 and 5 will require new in-stream structures environmental flow rules for Wingecarribee River Options 1, 2, 3a and 3b make a contribution to the objective Run-of-river transfers provide river flow connectivity past low-level structures and maintain stream flow through weir pools on the river RFO 10 Minimise effects of All options achieve the objective dams on water quality Wingecarribee Reservoir generally releases good quality water RFO 11 Ensure that the All options achieve this objective management of river Run-of-river transfers generally flows provides the mitigate the need for contingent necessary means to environmental flows to address water address contingent quality events environmental and water quality events RFO 12 Maintain or rehabilitate This objective is not applicable to the estuarine processes and options habitats Southern Highlands transfers do not affect estuaries
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
51 What are the next steps?
Economic and social assessments
Economic and social assessments of the potential Tallowa Dam environmental flow rules, dam operation options, and Southern Highlands transfer options are being undertaken to form part of the advice to Government. Feedback from the current consultation process will provide valuable input to these assessments.
These assessments consider the likely effects of options on individuals, groups and businesses that may conduct activities such as recreation, agriculture, tourism, fishing, and industry. This will include understanding how changes to the Shoalhaven Water Supply Transfer Scheme and new environmental flows might impact on community values.
Environmental flows process
As discussed earlier, the next step is to assess how the narrowed range of rules for the dam operation and environmental flows presented in this paper are likely to affect key ecological processes. A better understanding of the flow–ecology relationships will inform how the key social, economic and cultural heritage values identified by the community can be best addressed by the new environmental flow release rules.
Advice to Government
Following review of public submissions resulting from this discussion paper, and completion of any further technical or scientific work and economic and social assessments, SCA and DNR will provide advice to Government by the end of 2006 as follows:
Environmental flows
Advice will recommend a preferred environmental flow rule set informed by the water uses and values considered most important by the community, the outcomes of ongoing scientific investigations, and submissions received on this discussion paper.
Dam operations
Advice will recommend suitable arrangements for operating Tallowa Dam that balance environmental flow, community, and water system needs.
Transfer options
Advice will recommend a way forward for Southern Highlands transfer options including:
• a shorter list of options informed by environmental, community, and water system needs
• a process for developing and fully assessing the impacts of the shorter list of options
Shoalhaven Water Supply Transfers and Environmental Flows • a process for evaluating and selecting a preferred option, if necessary. Discussion Paper - August 2006
52 Implementation
Environmental flows
The new rules will be included in the draft Water Sharing Plan for the Greater Metropolitan Region, which will be released for community comment. A new water management licence will be issued by DNR to the SCA to implement the new active environmental flow rules.
Dam operations
Implementing new dam operation rules will depend on the breaking of the current drought and the implementation timetable of the above Water Sharing Plan’s new environmental flow rules.
Transfer options
Further development of the transfer options will be considered in response to feedback from this discussion paper and in the light of the future balance between water supply and demand as assessed during the regular reviews of the Metropolitan Water Plan.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
53 How can you be involved?
The Government seeks comment on any issues arising from the discussion paper and in particular the following: • your use of, or activities associated with:
• the Shoalhaven River downstream of Tallowa Dam or the Shoalhaven River estuary
• the Shoalhaven and Kangaroo rivers upstream of Tallowa Dam
• the Wingecarribee, Wollondilly or other affected Southern Highlands rivers and streams
• possible transfer pipeline routes.
• how you think these uses or activities might be affected by the different environmental flow, dam operations or transfer options
• any characteristics of the areas affected by the options that you consider valuable
• how you think these valuable characteristics might be affected by the different options.
You can give your feedback in any of the ways detailed below.
How you can have your say
Community comments and submissions are welcomed. They can be: • emailed to [email protected]
• mailed to Shoalhaven Community Consultation, Sydney Catchment Authority, PO Box 323 Penrith, NSW 2751
• provided on the phone by calling 1300 722 468
• submitted via an online feedback form on the SCA website at www.sca.nsw.gov.au
• faxed to (02) 4721 0951.
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
54 Glossary and acronyms
Active environmental water Water deliberately released through pipes and valves as environmental flows from the dam
CMA Catchment management authority
Contingent flows Flows that are released from a dam to meet a particular outcome in the downstream river environment
DNR Department of Natural Resources
Drawdown The operating range of a dam
Ecosystem A system made up of a community of animals, plants and bacteria and its interrelated physical and chemical environment
Environmental flows Water flowing from dams to provide a flow of water in a river, stream of other natural waterway to protect and improve river health
Estuary A semi-enclosed coastal body of water which has a free connection with the open sea and within which sea water mixes with fresh water
Fish passage The unrestricted movement of fish up and down stream
Freshes Substantial rises in the water level in the river for short periods after a rainfall event
Geomorphology The study of landforms and the processes which shape them
Gigalitre (GL) Volume equal to one billion litres or 1,000 megalitres (ML)
Greater Sydney Metropolitan Sydney, the Illawarra and the Blue Mountains
Groundwater All water found below ground level in saturated soils and rocks
Hydrological computer modelling Using a computer program to simulate a water related process or processes that occur in a catchment
Megalitre (ML)
Volume equal to one million litres Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
55 Minimum operating level The lowest level from which water can be extracted from a dam
MWP Metropolitan Water Plan
Operating storage The amount of water available for water supply in a lake or reservoir
Passive environmental water The water that naturally spills from a dam when it is full. Additional water to the active water released as environmental flows
Release rules Rules established to specify the size, duration, frequency, variability and seasonality of environmental flow releases
RFO River flow objective
Run-of-river transfers Water that is transferred using existing rivers and streams
SCA Sydney Catchment Authority
SCA total operating storage The total amount of water stored in all SCA dams that is available for water supply
SWC Sydney Water Corporation
Total storage The total volume of water that can be stored in a dam
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
56 Figure 11. Sydney’s drinking water catchments
Shoalhaven Water Supply Transfers and Environmental Flows Discussion Paper - August 2006
57 ShoalhavenShoalhaven RiverRiver
WaterWater SupplySupply TransfersTransfers andand EnvironmentalEnvironmental FlowsFlows
What if I want to know more?
The SCA and DNR will consult with the Shoalhaven community about the discussion paper in a number of ways.
The exhibition period opens on Monday 28 August and closes Friday 6 October 2006.
• Three community information and feedback sessions will be held during the exhibition period (see page 3 for details).
• Displays, with an information officer available, will rotate between Nowra, Bowral and Kangaroo Valley (see page 2 for details).
• A newsletter will be sent to local residents and will include details about the information sessions and other consultation opportunities.
• An email information service is available at [email protected]
• Advertisements will be placed in local papers about the display and the information sessions.
• The SCA’s website – www.sca.nsw.gov.au will let the community access the discussion paper, supporting reports and other information material and comment directly.
• A phone enquiry service is operating during business hours on 1300 722 468.
• Stakeholder briefings will be provided to local councils and a range of local interest groups.
SH001-08-06V1