High-flow environmental water releases for second half of year

Property owners in southern New South Wales are encouraged to monitor high-flow environmental water releases in the coming months.

Property owners along the Snowy River and the upper Murrumbidgee River and other stakeholders have been advised about upcoming water releases to maintain the rivers’ ecological health. Three high-flow environmental water releases from Jindabyne Dam will occur between mid-September and October this year, while a large release from Tantangara Dam is scheduled for 25 September.

“High-flow water releases are designed to better mimic the natural flow characteristics of Snowy Mountain rivers, including snowmelt and the ‘freshes’ that occurred before the construction of the Snowy Scheme, to improve the long-term health of these river systems,” NSW Department of Climate Change, Energy, the Environment and Water Director Asset Management and Performance, Aurelio Lindaya, said. “The largest event this year is a ‘flushing flow’ on 15 October, which is essential for developing a more defined river channel in the former riverbed to help return the Snowy River to a smaller, but healthy, montane river.”

The planned releases for the 2025-26 water year have been organised by the NSW Department of Climate Change, Energy, the Environment and Water (DCCEEW) in close consultation with the Snowy Advisory Committee and Snowy Hydro. They include:

17 September 2025 – daily flow of 2,000 ML/d over 24 hours, with equivalent peak flow 3,000 ML/d for eight hours from 8 am to 4 pm
25 September 2025 – 1,700ML/day will be released from Tantangara Dam into the upper Murrumbidgee River, starting at midday for 24 hours. The plan also includes smaller, frequent releases throughout the water year.
2 October 2025 – daily flow of 3,500 ML/d over 24 hours, with equivalent peak flow 4,500 ML/d for eight hours from 8 am to 4 pm
15 October 2025 – daily flow of 5,000 ML/d over 24 hours with equivalent peak flow of 9,000 ML/d for eight hours from 8 am to 4 pm, if Jindabyne Dam levels are high enough to enable delivery via the spillway. Alternatively, the flow will be reduced to 5,000 ML/d delivered via the cone valves at a constant rate for 24 hours.

“We will also conduct frequent smaller releases throughout the year, which improve river health by establishing a new channel, wetting the riparian zones, and promoting aquatic and riparian vegetation,” Lindaya said. “Downstream landholders and visitors are encouraged to prepare for the water releases by securing watercraft and moving stock, pumps, and infrastructure to higher ground, while remaining aware of flow conditions.”

These annual flows are necessary to flush the riverbed of sediment, which will provide seasonally appropriate habitat for fish, frogs, and platypus, as well as their food sources, such as invertebrates and crustaceans. In addition to the large flow releases, frequent smaller releases will be made throughout the year.

High-flow environmental water releases improve the health of the river by flushing fine sediment and improving connectivity. They also provide opportunities for fish and other native animals to move and wet and fill riverside wetland areas.

“Until now, environmental releases have been capped at 1,500 ML/d due to infrastructure and operational constraints, but this year we are trialling a larger flow of 1,700 ML/d to move more sediment off cobbles, improving fish passage and habitat for Macquarie perch spawning,” Lindaya said. “Snowy Hydro is working to address these constraints, and the NSW Government is conducting a risk assessment to ensure we achieve the right balance.”

Elevated flows will occur on the days leading up to and following the release to create a more natural flow release pattern (hydrograph) that maximises ecological benefits.

The NSW Government is committed to informing the public and will issue reminders closer to each event. It is also important to note that the plan is subject to change, depending on weather, operational and environmental conditions.

In addition to the planned releases, other initiatives are being trialled to support the health of the Snowy River. This includes a pulse of water released in January, followed by smaller flows, to flush pools along the river and combat the mouth of the river closing during dry conditions.

“Previous studies show that Snowy montane rivers respond well to these seasonal high-flow events, and this approach has received support from the Snowy Advisory Committee and ecological experts,” Lindaya said. “We remind downstream landholders and visitors to take appropriate precautions before the water releases, including securing watercraft and moving stock, pumps, and infrastructure to higher ground.”

As an outcome of the Snowy Water Licence Review, flexible delivery of smaller flows will also continue, enabling the volume and timing of releases under 2,500 ML per day to quickly change to respond to natural cues such as rainfall events.

Please check the DCCEEW website for any changes closer to each planned event at: Snowy River increased flows.