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Environmental flow management

Snowy Montane Rivers Increased Flows

Read about environmental releases from Tantangara Dam into the upper Murrumbidgee and other montane rivers.

Thredbo to Mount Kosciuszko walk, alpine stream - Image credit: E Sheargold/DPE

About Snowy Montane Rivers Increased Flows

The Snowy Water Inquiry Outcomes Implementation Deed (SWIOID) provides for environmental releases into a number of high altitude (montane) rivers whose flows are significantly affected by the operation of the Snowy Scheme.  The Snowy Montane rivers are:

  • the Snowy River above Jindabyne Dam
  • the Goodradigbee River
  • the Murrumbidgee River below Tantangara Dam
  • the Geehi River.

Read more about the legislative context and the background to the environmental reforms and water recovery achieved through the Snowy Water Initiative.

Environmental water priorities

The Snowy Montane Rivers Increased Flows (SMRIF) program is managed by the NSW Department of Climate Change, Energy, the Environment and Water – Biodiversity, Conservation and Science (DCCEEW BCS) in consultation with the Snowy Advisory Committee, DCCEEW-Water and Snowy Hydro.

You can find an explanation of the SMRIF program annual priorities and the ‘Annual environmental water priorities in the Snowy and Snowy montane rivers’ at the DCCEEW BCS website.

Annual targets for the 2024-25 water year

See the 2024-25 annual targets for the Snowy Montane Rivers in the table below.
Increased flowsRelease location2024-25
annual volume (GL)
Murrumbidgee River at TantangaraTantangara Dam35.090
Goodradigbee RiverGoodradigbee Weir7
Geehi RiverMiddle Creek Weir
Strzelecki Creek Weir
Snowy River – below Island BendToolbar Creek
Diggers Creek Weir
Snowy River - below Guthega Dam Falls Creek Weir 3.4

Releases into the upper Murrumbidgee for the 2024–2025 water year

A total of 35,080 megalitres (ML) of environmental water will be released to the Upper Murrumbidgee River below Tantangara Dam during the 2024–25 Snowy water year (from 1 May 2024 to 30 April 2025).

The SMRIF release pattern has been designed to include frequent small releases, two moderate releases in excess of 1000 ML/day and one large “high-flow” release of 1,500 ML/d in September 2024.

In total over the year there will be 8 days where flows will be above 500 ML/d across 3 peak events, including 4 days of high flows above 1,000 ML to move fine sediment and inundate low lying benches.

Continuous releases will be made between 1 May 2024 and 4 January 2025 and between 27 March and 30 April.

A series of small ‘freshes’ will also be provided from January to March 2025 to recharge the system between periods of zero environmental release.

During periods of no scheduled environmental releases, Snowy Hydro is required to make releases to maintain flows at or above 32 ML/day at Mittagang Crossing, if tributary flows do not provide this level of flow.

The planned high-flow release for the 2024-25 water year is shown in the table below. “High flow” releases are those in excess of 1,400 ML/day, which is the threshold above which flows may have the potential to create safety risks, based on local risk knowledge and experience from past releases.

Release dateRelease peak
Tuesday 24  September1,500 ML/day starting from midday for 24 hours

Note: Dates and volumes of these high-flows may change subject to environmental, climatic or operational conditions. A series of smaller release will also be made.

Design rationale for environmental releases

Water releases are designed to better mimic the natural flow characteristics that are seen in Snowy montane rivers, with the aim of improving the long-term health of these river systems.

High-flow environmental water releases improve the health of the upper Murrumbidgee River by flushing sediment, clearing vegetation that encroaches into the channel, providing opportunities for fish and other native animals to move, and wetting and filling riverside wetland areas.

A series of smaller flow peaks has been demonstrated to make better use of the available water improve river health by to establishing a new smaller channel, wetting the riparian zone and promoting the establishment of aquatic and riparian vegetation.

Temporary water restrictions

Unregulated licence holders in the Murrumbidgee I and II water sources cannot take water if flows at their nominated gauge are below the temporarily raised access thresholds published in the order for that day. Details on the raised access thresholds and how to comply can be found on WaterInsights page:

The commence to pump guide (https://waterinsights.waternsw.com.au/api/water-source/v2/updates/2758/attachment) on those pages also explains that if flows are above the raised access thresholds, these unregulated licence holders can take water.

Stock and domestic licence holders and water users with basic landholder rights can continue to take water during the environmental flow release.

Safe management of high flows

The department works with Snowy Hydro and other relevant agencies to ensure the safe management of high flow releases from Tantangara Dam into the upper Murrumbidgee River. The Snowy Montane Rivers Increased Flows – Safety Management Plan 2022-2027 (PDF, 1137.67 KB) details the processes that are followed. This Plan is reviewed annual for currency.

Rising river alerts for 2024-25 water year

The department will publish a ‘rising river alert’ below and issue it to relevant media organisations several days prior to the high-flow event.