Upper Murrumbidgee River increased flows
In determining how to use the environmental water recovered for the Snowy River through the Snowy Water Initiative, the New South Wales, Victorian and Commonwealth governments jointly agreed that ecological objectives would be achieved by storing and then releasing sufficient volumes to provide annual flushing flows.
Similar to the Snowy River, when there is sufficient environmental water available, a modified ‘flow scaling’ approach has been applied to the Murrumbidgee River to assist in providing natural seasonality and daily variability.
These high flows facilitate the improvement in the physical condition of the in-stream habitat by scouring and transporting fine sediment (i.e. primarily, sand, silt and clay). Meeting ecological objectives was identified as a high priority during the Snowy Water Inquiry.
High flows are important to improve river health. It is expected that as the river physically responds over time to the higher flows, the focus of the recovery process will transition to meet other ecological objectives.
2022–2023 water year
A total of 35,773 megalitres of environmental water will be released to the Upper Murrumbidgee River below Tantangara Dam during the 2022–23 water year, including three separate high-flow events.
The 2022–23 release strategy uses the natural flow-scaling approach to deliver three flood pulse events with flow peaks greater than 1,000 megalitres (ML)/d, but less than to 2,000 ML/d from the Tantangara Dam, through a manually operated outlet valve.
The Snowy and Montane River Increased Flows (SMRIF) release pattern has been designed to include three high-flow events from Tantangara Dam into the Upper Murrumbidgee River. These high-flow releases are designed to more closely mimic the natural characteristics of the Murrumbidgee River, including snowmelt and ‘freshes’ that occurred before the construction of the Snowy Mountains Scheme.
There will be no environmental flow released from Tantangara for 20 periods totalling 140 days, as there is insufficient water available to maintain the flow regime for every day of the year that includes multiple high peaks. During this time, Snowy Hydro Limited 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.
|Thursday 23 June||Daily peak flow of 1,025 megalitres per day (ML/d) over 24 hours|
|Wednesday 27 July||Daily peak flow of 1,300 ML/d over 24 hours|
|Tuesday 11 October||Daily peak flow of 1,500 ML/d over 24 hours|
Note: The peak flow releases will occur over 24 hour period, commencing at 12:00pm (midday) Eastern Standard Time. The release date for these flow peaks could change as they are weather-dependent.
The releases to the Murrumbidgee River will be above 1,000 megalitres per day for 3 days.
The department will issue 'rising river alerts' to relevant media organisations several days prior to each of the three high-flow events.
Increased flows and targets
- Upper Murrumbidgee environmental flows to commence late – June
- Snowy Montane Rivers Increased Flows – Safety Management Plan 2022-2027
- Snowy Montane Rivers Increased Flows – 2022 Operations Plan
- Upper Murrumbidgee River high-flows 2022 – Frequently Asked Questions