Connectivity, habitat maintenance and support for native plants and animals including fish and frogs were the focus of releases for the Snowy montane rivers in 2024–25.
Key outcomes
Under dry to moderate conditions, environmental water managers worked with partner agencies and stakeholders to coordinate the delivery of water for the environment to:
- provide variable flows to the Snowy and Upper Murrumbidgee rivers, with higher releases during winter and spring, typical of snowmelt rivers
- improve the condition of the Snowy River channel and provide suitable habitat for water-dependent animals such as macroinvertebrates and native fish
- provide habitat diversity and increase resource availability and productivity for water-dependent animals including macroinvertebrates, frogs, platypus, turtles and fish, as well as provide opportunities for breeding and recruitment
- inundate wetlands and ponds to provide breeding opportunities for several native frog species including the whistling tree frog (Litoria verreauxii)
- facilitate connectivity along multiple rivers including the Snowy, Upper Murrumbidgee, Geehi and Goodradigbee rivers
- commence trigger flow trials in the Snowy and Upper Murrumbidgee River to provide flow flexibility in response to catchment conditions.
Catchment conditions
The Snowy and Snowy montane regions were drier than average in 2024–25.
Average rainfall in the southern Murray–Darling Basin in 2023–24 provided an overall water allocation of 264,900 megalitres for the Snowy and Snowy montane rivers in 2024–25.
The pattern for environmental water releases included higher flow rates over winter, spring and early summer. This reflects flow patterns typical of the mixed rainfall and snowmelt river system.
Partnering with Aboriginal peoples
Water for Country represents the planning and delivery of environmental water by the Department of Climate Change, Energy, the Environment and Water in collaboration with Aboriginal people across New South Wales. This work continues to progress, supporting ecological outcomes while also protecting and revitalising cultural places, values and interests.
Environmental water managers and the Snowy Advisory Committee continue to work with Aboriginal people to develop respectful and meaningful relationships to better understand cultural values for the Snowy and montane rivers. Work has started in the Upper Murrumbidgee, with Wolgalu and Ngunnawal peoples participating in the wider Murray–Lower Darling Rivers Indigenous Nations-led Murrumbidgee cultural exchange gatherings at Gayini.
Watering aims
Under a moderate resource availability scenario, environmental water managers and the Snowy Advisory Committee for the Snowy and Snowy montane catchments developed the annual plan for the Snowy and montane rivers increased flows 2024–25.
Aims for the use of water for the environment were to:
- continue to facilitate the rehabilitation and evolution of the Snowy River below Jindabyne Dam, and the Murrumbidgee River below Tantangara Dam into smaller, healthy montane rivers
- provide daily variable flows for the Snowy and Upper Murrumbidgee rivers with higher release rates during winter and spring
- improve the Snowy River channel condition by providing several high flow events to reduce fine sediment and algae smothering, and clean riffles, cobbles and gravel by mobilising sediments
- provide 3 high-flow releases of 1,200 megalitres or more in the Upper Murrumbidgee River to flush gravels and cobbles and improve habitat in the lead up to the Macquarie perch (Macquaria australasica) breeding season
- inundate and connect low-level ponds and back water areas during late winter and spring, and provide freshes in summer to support breeding and recruitment opportunities for flow-dependent frog species and other native water-dependent animals
- provide natural daily flows to targeted Snowy montane streams to provide connectivity and maintain ecological functions.
With moderate rainfall and high environmental water allocations, environmental water managers provided improved opportunities for water-dependent native plants and animals to breed, move and thrive in the Snowy and Snowy montane catchments.
Water delivery
This table and chart provide a summary of 264,900 megalitres of water for the environment delivered in the Snowy and Snowy montane catchments during the 2024–25 water year.
Figures were accurate at the date of publishing but may be adjusted. Watering event numbers in the table and bar chart relate to location numbers marked on the map.
Notes: EWA = environmental water allowance accrued under the Snowy Water Inquiry Outcomes Implementation Deed.
| Watering event number | Event name | Outcomes | Start date | Finish date |
|---|---|---|---|---|
| 1 | Snowy River | Connectivity | 1 May 2024 | 30 April 2025 |
| 2 | Upper Murrumbidgee | Connectivity, native fish | 1 May 2024 | 30 April 2025 |
| 3 | Montane Streams | Connectivity | 1 May 2024 | 30 April 2025 |
Outcomes
In 2024–25, environmental water managers worked with Snowy Hydro and other stakeholders to deliver water for the environment to the Snowy, Upper Murrumbidgee, Geehi and Goodradigbee rivers. Environmental flows supported river connectivity to improve river health and provided important habitat for water-dependent native plants and animals, including frogs, platypus and fish.
High flows helped flush sediment and cleaned riffles to improve instream habitat.
The high flows played a crucial role in connecting ponds and small wetlands along the Snowy and Upper Murrumbidgee rivers. Connection of these habitats supported breeding activities for a diversity of frog species. Water managers conducted frog monitoring and found 8 frog species, including the endangered alpine tree frog (Litoria verreauxii alpina).
The alpine tree frog, a subspecies of the broadly distributed whistling tree frog, was found along the Upper Murrumbidgee and Upper Snowy rivers. This species occurs in alpine and sub-alpine zones or high country in south-eastern New South Wales and Victoria, usually above 1,100 metres and mostly located within Kosciuszko National Park.
Case study: trigger flow trials
A 3-year trial introducing flexible trigger flows in the Snowy and Upper Murrumbidgee rivers started in 2024–25. This new approach, an outcome of the last Snowy Water Licence Review, will allow for adaptive releases that respond to natural cues on up to 4 occasions for the Snowy and Upper Murrumbidgee rivers.
Under current licence arrangements, daily flow patterns from May to April are planned and agreed on before the start of each water year. This trial is a significant first step towards adaptive management, which aims to enhance system health and support water-dependent ecosystems, particularly productivity and native fish species.
Flexible trigger flow releases are a form of adaptive management widely used in environmental watering programs across other river systems. Under this trial, the timing of water releases is adjusted based on natural rainfall events. Specifically, the largest monthly planned flow, typically scheduled for the 25th day of the nominated month, will be rescheduled if streamflow triggers are met naturally.
These triggers are based on data from upstream gauges and respond to significant runoff events. Monthly flow levels or thresholds are based on data from the past 10 years. This enables us to work out when flow levels are higher than usual. Triggers are met when there is enough water flowing or when the flow rises at key gauge points upstream of storage.
When a trigger is activated, multiple organisations collaborate to assess flood risk and coordinate a timely response within 48 hours. This includes Snowy Hydro Limited, Bureau of Meteorology and the department.
In 2024–25, triggers were met several times in both the Snowy and Upper Murrumbidgee systems. This resulted in environmental releases that aligned with natural tributary flows downstream of dams. These events demonstrated the potential of flexible flows to enhance ecological outcomes.
The trial continues to be reviewed and refined, with the goal of establishing long-term adaptive water management.
