The Snowy Advisory Committee met in Cooma for the first time in more than 2 years. The Committee reflected on the 2021-22 water year, reviewed environmental water delivery so far for 2022-23 and received multiple presentations on externally funded projects being implemented to support the program.
The 2021–22 Snowy and montane rivers environmental watering program
Continuing wet conditions, including the wettest December on record, saw Jindabyne Dam close to spilling in mid-December 2021. For the first time, the planned Snowy Rivers Increased Flows (SRIF) releases were changed by bringing 10 GL forward from the remainder of the water year for delivery in December. These changes to the release pattern aimed to mitigate the risks of an uncontrolled spill while also providing an opportunity to deliver environmental water in time with natural cues, reflecting the wet conditions.
The Jindabyne catchment continued to receive high rainfall, and the dam spilt on 19/20 December 2021, followed by a number of pre-releases (controlled spills) for the remainder of the 2021–22 water year to help reduce the risk of further uncontrolled spills.
Approximately 294 GL was released from Jindabyne Dam into the Snowy River, including 209 GL of Snowy Rivers Increased Flows and 85 GL of spill/pre-releases. Included in the spill volume was 18.7GL of Snowy Rivers Increased Flows 'borrow' that has been agreed to be repaid in 2022–23.
Upper Murrumbidgee River
Releases from Tantangara Dam into the upper Murrumbidgee remained on track for the water year, delivering 31.8 GL of water for the environment. The released flow included three peaks of at least 1GL/day to help mobilise fine sediment and provide suitable habitat for native fish and frogs.
Daily environmental releases to the targeted montane streams for 2021-22 included the Snowy River above Jindabyne Dam, the Goodradigbee River and the Geehi River. Releases remained within target.
The monitoring program now includes frogs, water temperature, water quality and surveillance cameras, and macroinvertebrates. The Department of Planning and Environment-Water and NSW National Parks and Wildlife Services assisted with monitoring activities, allowing the expansion of the program.
Secured funding provided opportunities to further support the monitoring program. This included geomorphology surveys in the Snowy River and habitat assessments in the upper Murrumbidgee.
The information and data collected through the monitoring projects will help the Committee to provide future advice on the planned releases for the Snowy and montane rivers.
Snowy River geomorphic study
Teresa Rose from Riverrose consulting presented the latest results from a geomorphic study looking at changes to the riverbed formation. The project is repeating a previous study undertaken in 2012 undertaken from below Jindabyne Dam to the Dalgety uplands.
The results indicate that the Snowy River channel is deepening over time, while the rate of channel widening is variable across sites. The results are promising and indicate that environmental flows support the long-term objective of having a smaller but healthy Snowy River.
Snowy River geomorphic study
Duanne White from the University of Canberra presented the upper Murrumbidgee 'habitat and barrier mapping project' results to the Committee. The project identifies large barriers impacting Macquarie perch movement in key breeding areas located from Tantangara to the Numeralla River junction. Lidar, aerial imagery, on-ground surveys and community consultation are being incorporated to assist in the identification of important barriers.
The next stage of the project is to observe the barriers during environmental releases to see what role environmental water can play to drown out the barriers to allow for fish passage.
Environmental water releases for the 2022-23
The new water year commenced on 1 May. So far, environmental water releases are tracking well for the Snowy River, montane streams and the upper Murrumbidgee.
Jindabyne Dam remains close to full, and Snowy Hydro will consider conducting pre-releases to reduce the risks of an uncontrolled spill. The Department of Planning and Environment and the Committee plan to provide input into the design of any pre-releases to maximise the ecological benefits.
Field to Tantangara Dam
The Committee visited Tantangara Dam to get a firsthand look at how the dam operates, including the limitations for flow delivery into the upper Murrumbidgee. The Committee were also provided with an update on the Snowy 2.0 project.
Snowy Advisory Committee Strategic Planning Workshop
Consultant Richard Baker held a workshop with the Committee on 26 May. The workshop aimed to identify the values of the Snowy River and montane rivers to inform the development of the Strategic Plan. The plan will include the Committee's vision for the Snowy and montane environmental watering program and help guide future decision making.
The Committee next plans to meet in August 2022.