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 – Conservation Programs, Heritage and Regulation Group (DCCEEW-CPHR) 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-CPHR website.
Annual SMRIF targets for the 2026-27 water year
For the 2026-27 water year, the New South Wales, Victorian and Commonwealth governments have committed 92.8 GWh, equivalent to 63,300 megalitres (ML), to be released as SMRIF, including 6,294 ML from Tantangara Dam into the upper Murrumbidgee River.
| Increased flows | Release location | 2026-27 annual volume (ML) |
|---|---|---|
| Murrumbidgee River at Tantangara | Tantangara Dam | 6,294 |
| Goodradigbee River | Goodradigbee Weir | 12,000 |
| Geehi River | Middle Creek Weir Strzelecki Creek Weir | 17,500 5,200 |
| Snowy River – below Island Bend | Toolbar Creek Diggers Creek Weir | 9,500 9,400 |
| Snowy River - below Guthega Dam | Falls Creek Weir and minor diversion structures | 3,400 |
SMRIF will be delivered from modified weirs to montane streams including the Snowy River above Jindabyne Dam, the Goodradigbee River and the Geehi River. All the delivery points will be set to allow full passing flows, meaning no water is diverted from these rivers to the Snowy Hydro scheme.
Releases into the upper Murrumbidgee for the 2026–2027 water year
A total of 6,294 ML of environmental water will be released to the upper Murrumbidgee River from Tantangara Dam during the 2026–27 Snowy water year (1 May 2026 to 30 April 2027). This is lower than last year due to drier conditions causing lower water allocations to be accrued against environmental water entitlement.
The flow regime has been designed to maximise environmental outcomes from the available water:
- While there are no planned high flow releases like in previous years (in excess of 1,400 ML/d) due to lower water allocations, there will be 5 small flow pulses ranging in size from 150 to 450 ML/d that will be released in winter and spring, reflecting the natural timing of expected peak events to provide flow variation and support the health of the river.
- The largest flow of the year will be 450 ML/d on 25 September 2026. This is a flexible release event and may be bought forward to earlier in the month to respond to natural cues.
- In addition to the 5 small flow pulses, smaller releases are planned throughout the year.
- There will be periods throughout the year where no environmental flows will be released from Tantangara Dam because there is insufficient water available to maintain a variable flow regime for every day of the year. During this time, Snowy Hydro may make riparian releases to maintain flows at or above 32 ML/d at Mittagang Crossing if tributary flows do not provide this level of flow, consistent with the rules of the Snowy Water Licence.
The communication and engagement activities to support safe, informed and inclusive implementation of these releases are outlined in the SMRIF Safety Management Plan.
Flexibility of smaller releases
Flexible delivery of smaller flows was introduced in 2024–25, whereby the date of some releases may be changed to respond to natural cues such as rainfall events. This trial will continue throughout 2026-27 to help support river health and water dependant plants and animals including native fish.
This means that the volume and timing of planned releases may change without notice. This adaptive management approach is commonly applied in other rivers’ environmental watering programs.
The trial is being implemented through an agreed Operating Protocol (PDF, 133.38 KB).
Environmental objectives of flows
Due to the reduction of natural flows resulting from the Snowy Scheme, the upper Murrumbidgee River is largely reliant on rainfall and tributary inflows downstream of the dam for ecological functions.
Where possible with available water, environmental releases are designed to mimic the natural flow characteristics that are seen in Snowy Mountain rivers with the aim of improving the long-term health of these river systems.
Higher releases are generally planned over winter and spring, to mimic snowmelt and ‘freshes’ that occurred before the construction of the Snowy scheme.
There are generally periods of lower flow in summer and autumn, reflecting the naturally drier conditions that occur.
This year, like in most years, there is insufficient water available to provide daily releases while also maintaining flow variation, which is critical to support a healthy montane river. Similar to previous years, there will be periods of no planned releases, and a series of small variable flows to help support in part river health and function by providing some natural flow variability.
Environmental releases from Tantangara Dam aim to provide some support to:
- instream habitat for water dependant plants and animals, including macroinvertebrates and the food web of fish, frogs, platypus and rakali
- hydrology by providing some flow variability with higher winter and spring flow rates to partially mimic a snowmelt river
- channel morphology (sediment), with small peaks to mobilise sediment and clean riffles. Due to the small volume of available water, benefits will depend on coinciding with natural flow events
- native fish such as the endangered Macquarie perch, which are present downstream of Yaouk
- water dependant flora and fauna by providing some flow variability to promote vegetation that supports water-dependent animals, such as platypus and frogs.
Protection of SMRIF
When conditions are dry, changes to access conditions for Murrumbidgee I and II licence holders may be announced on WaterInsights to ensure that SMRIF is protected. These announcements are enabled under the Water Sharing Plan for the Murrumbidgee Unregulated River Water Sources 2025 and can be found at:
Licences for town water supply and water users with basic landholder rights are not affected by these announcements.
Safe management of high flows
The release of environmental water into the Snowy montane rivers has been successfully trialled since 2011.
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 SMRIF Safety Management Plan details the processes that are followed. This plan is reviewed annual for currency.
Individual landholders should take all necessary precautions with stock and property, both before and during the additional flows. This may involve moving any assets away from the bank of the river.
Rising river alerts
There are no planned high-flow releases (in excess of 1,400 ML/d) during the 2026/27 water year due to lower water allocations, therefore there will be no ‘rising river alerts’ issued.
Environmental flow presentations
Community meetings were held in Bredbo (September 2024) and Cooma (August 2025) to discuss the program's benefits, key participants and safety management of environmental flows. Recordings of the 2024 presentations are available below.
FAQS
High-flow events are releases of 1,400 ML/d or greater. This is the flow threshold at which the department and Safety Technical Advisory Committee consider that potential safety risks may begin to occur, based on local knowledge and evidence from past releases. For flows of 1,400 ML/d or greater, the department instigates the processes set out in the Safety Management Plan including extensive public communications.
The threshold has been incrementally increased from 1,000 ML/d to 1,300 ML/day and now to 1,400 ML/d as evidence from past releases has been collected.
Changes to the definition of high-flow over recent years mean that less releases are classified as ‘high-flow” events for safety management purposes. As evidence has been gained over time, the department has increased the definition of a ‘high-flow’ from 1,000 ML/d to 1,400 ML/d.
There are no planned high flow releases like in previous years because of drier conditions, causing lower water allocations to be accrued against environmental water entitlement. There will be several smaller pulses to help provide flow variability and support the health of the river.
The volume and timing of high-flow environmental flow releases (in excess of 1,400 ML/d) for the upcoming water year are listed on the department’s website. All daily release volumes are listed on Snowy Hydro’s website.
Each high-flow event will commence at 12pm (midday) local time for a 24-hour period.
For the high-flow releases, the days leading up to and following the release will have intermediate flows to create a more natural flow release pattern (hydrograph) that maximises ecological benefits.
The water will be released into the upper Murrumbidgee River from Tantangara Dam and travel down the river, through the ACT and continue until it enters Lake Burrinjuck, NSW.
In addition to the high-flow releases, frequent moderate and smaller releases are made throughout the year. These are listed on Snowy Hydro’s website.
As an outcome of the Snowy Water Licence Review, flexible delivery of smaller flows was introduced last year on a trial basis, whereby the date of some releases may be changed to respond to natural cues such as rainfall events. This trial will continue throughout 2026/27 to help support river health and water dependant plants and animals including native fish.
This adaptive management approach is commonly applied in other rivers’ environmental watering programs.
This means that for releases under 1,400 ML/d, the volume and timing of planned releases may change without notice. Flexible delivery will not apply to high-flow events (i.e. greater than 1,400 ML/day) for the 2026/27 water year.
Delivering flows in response to natural cues aims to give dam releases a better chance to combine with rainfall-driven tributary inflows across the upper Murrumbidgee River catchment. This assists healthy river health and water dependant plants and animals, including native fish.
Flexible delivery will not apply to high-flow events (i.e. greater than 1,400 ML/d) for the 2026/27 water year, although we may move towards greater flexibility of high-flow events in the future. Appropriate safety management planning would be developed to support this.
There will be periods throughout the year where no environmental flows are released from Tantangara Dam. This is because there is insufficient allocated water available to maintain a variable flow regime (including multiple large releases) for every day of the year. During this time, Snowy Hydro is required to make releases to maintain flows at or above 32 ML/d at Mittagang Crossing if tributary inflows do not provide this level of flow, subject to the rules of the Snowy Water Licence.
Planned flows may be modified or cancelled subject to climatic environmental or operational conditions near to the time of release. The department will endeavour to inform the public of changes to high-flow releases, where possible. Whilst the volumes of smaller releases are also planned at the start of the year, the volumes of smaller releases (less than 1,400 ML/d) may be changed at any time without notice. This allows greater flexibility in the delivery of environmental releases, which provides improves environmental outcomes.
Natural inflows from tributaries will generally have a significantly larger influence on river flow rates, water levels and ecosystem processes than the environmental flows, particularly further downstream. The influence will be more significant in wetter years with more natural runoff.
Rising water levels may result from a combination of the environmental releases and natural tributary inflows. The combination of varying release volumes and natural conditions means that the peak flows in the river will vary from year to year.
The peak will naturally reduce as it progresses downstream, but the pulse could still be detectable near the ACT border at Lobbs Hole and below.
The rise in water levels will vary depending on your location and inflows from tributaries, but flows are intended to remain within the river channel. In confined gorge reaches, the water level increase could be greater than elsewhere.
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 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.
The long-term aim of upper Murrumbidgee environmental flows is to restore the section of river below Tantangara Dam to a smaller yet ecologically healthy system. The water releases help mobilise fine sediment and inundation of lower lying connected ponds to provide habitat for water dependent species. The intent is to reshape a smaller channel within the former Murrumbidgee riverbed to improve instream habitat for aquatic biota.
The flow pattern is designed to better mimic the natural flow characteristics that are typically seen in Snowy montane rivers. This flow pattern incorporates a high degree of natural seasonality and daily variability, while still maintaining natural high-flow events in the Murrumbidgee. High-flow events allow the river to re-establish stream function and improve the in-stream habitat.
High-flow events wet the riparian zone, promoting the establishment of aquatic and riparian vegetation and providing important habitat for water dependent animals, including native fish, waterbugs, frogs and platypus.
The environmental water release strategy attempts to mimic the natural hydrological characteristics of the upper Murrumbidgee River. Before the Snowy Scheme was constructed, high-flow events during winter and spring were commonplace.
Historically, the flow regime of the upper Murrumbidgee River at Tantangara showed a greater frequency of flood peaks during winter and spring.
The smaller winter flow peaks were typically associated with the passage of cold fronts delivering rain to lower elevation catchments and snow to higher elevations.
A series of smaller flow releases has been demonstrated to improve river health by establishing a new smaller channel, wetting the riparian zone and promoting the establishment of aquatic and riparian vegetation.
There is a high degree of daily flow variability with complex multi-peak hydrographs that are typical of rivers in the Snowy Mountain.
The NSW, Victorian and Commonwealth governments agreed the amount of water allocated to the entitlement each year is subject to the amount of rainfall, snowmelt and inflows into the southern Murray-Darling Basin storage dams.
Wetter conditions and stronger inflows across the southern Murray-Darling Basin may generate larger volumes of water for environmental flows. Drier years result in lower allocations and therefore less water for the environment.
Members of the public are reminded that they should exercise their own judgment about the safety of any viewing site based on the conditions on the day.
Recreational use of the river during the period in which the high flows are taking place is not recommended. These high-flow events are considered unsafe for recreational water activities as the flows may create strong and dangerous currents and could dislodge debris in the river.
Individual landholders should take all necessary precautions with stock and property, both before and during the additional flows. This may involve moving any assets away from the bank of the river.
The NSW Government recommends that equipment should be secured or elevated 3 metres higher than the existing base water level in the Murrumbidgee River.
The NSW Department of Climate Change, Energy, the Environment and Water works with Snowy Hydro, local councils, the State Emergency Service, the Bureau of Meteorology and other key stakeholders to review risks prior to high flow releases. Flows may be modified or cancelled with short notice if risks are deemed unacceptable. We encourage the public to check our website for any changes closer to the scheduled events.