VEWH - Snowy River

There are four major dams and multiple diversion weirs in the upper Snowy River catchment that capture and divert water to the Murrumbidgee and Murray River valleys. The hydrological effects of the Snowy Mountains Scheme are substantial, but they are partly alleviated by the contribution of flows from tributaries (such as the Delegate River in NSW and the Buchan and Brodribb rivers in Victoria).

The construction and operation of the Snowy Mountains Hydro-electric Scheme previously diverted 99 percent of the Snowy River’s mean annual natural flow at Jindabyne. The loss of flow changed the structure and function of the river, reduced the opening of the Snowy River entrance to Bass Strait and resulted in a decline in environmental values.

The Victorian, NSW and Commonwealth governments agreed to recover some of the water and in 2002 delivered the first environmental flow to the Snowy River below Jindabyne Dam to help restore the damage done by decades of limited flow. The Victorian share of water for the environment available for use in the Snowy system is held in the Victorian Murray, Goulburn and Loddon systems. The NSW share of water for the environment available for use in the Snowy system is held in the NSW Murray and Murrumbidgee systems. Collectively, the water is made available for environmental flows in the

Snowy River via a substitution method, whereby water for the environment allocated in Victoria and NSW replaces water that was earmarked for transfer from the Snowy to Victoria and NSW to support irrigation demands. The NSW Department of Planning and Environment plans environmental flows in the Snowy River in consultation with the Snowy Advisory Committee. The committee includes representatives of the Aboriginal community, local community, the Victorian Government, NSW Government and environmental experts. The committee brings together local knowledge and expert advice to help inform the management and delivery of water for environmental outcomes.

The water year in the Snowy system runs from 1 May to 30 April, and the daily flow regime is planned in advance by the Snowy Advisory Committee. Water for the environment is delivered daily to the Snowy River below Jindabyne Dam. The annual allocation of water for the environment varies based on water availability, rainfall and inflows. Environmental releases aim to deliver an average of 212,000 ML per year, the equivalent to 21 percent of the average annual natural flows before the construction of the Jindabyne Dam.

System map

Snowy System SWP — Grey river reaches have been included for context. The numbered reaches indicate where relevant environmental flow studies have been undertaken. Coloured reaches can receive environmental water.

Environmental values

Environmental values in the upper reaches and tributaries of the Snowy River include water-dependant plants and animals, including freshwater native fish (such as river blackfish and Australian grayling), platypus and frogs. The lower reaches support estuary perch and Australian bass that move between saltwater and freshwater systems. The estuary contains estuarine and saltwater species (such as flathead and black bream). The floodplain wetlands of the Snowy River near Marlo provide feeding and breeding areas for wetland and migratory birds.

Recent conditions

Rainfall in the Snowy River catchment in 2021-22 was significantly above the long-term average, with some areas receiving their highest recorded monthly totals. Jindabyne Dam spilled in December 2021, and the storage manager made several airspace releases over subsequent months. These spills and natural inflows from downstream tributaries delivered regular floods in the lower Snowy River during the year. Flows peaked above 20,000 ML per day in the lower Snowy River several times during winter, spring, summer and autumn. The December flood peaked at 130,000 ML per day at Jarrahmond, near Orbost.

Water availability for environmental flows in the Snowy River is determined by allocations in the Murray, Goulburn, Loddon and Murrumbidgee rivers. In 2021-22, 209,577 ML1 was allocated for environmental releases in the Snowy River system. This was the highest allocation since 2011 and more than twice the 2020-21 allocation of 91,176 ML.

The high allocation allowed river managers to deliver larger flows for longer durations than 2020-21. Five winter/spring high- flow events were released (one more than in 2020-21), and a flushing flow occurred in October 2021.

Environmental monitoring in the lower reaches of the Snowy River and its estuary over the last decade indicates that environmental flows are improving physical and ecological processes, increasing ecosystem productivity and improving aquatic habitat. Extensive bushfires in December 2019 and January 2020 affected most of the Snowy catchment. Although rivers and streams had poor water quality, particularly after heavy rain events, in-stream and riparian vegetation are beginning to regenerate. It will take years for the catchment to recover from impacts of this scale.

Scope of environmental watering

The total volume available for release to the Snowy River in 2022-23 is 205,110 ML. That is one of the highest volumes of water for the environment ever available for the Snowy River.

Due to operating rules in the system, the daily flow regime that will be delivered in 2022-23 is pre-planned. The storage manager will make daily releases of varying magnitudes from Lake Jindabyne between May 2022 and April 2023 to mimic the typical flow patterns of a mixed snowmelt/rainfall river system characteristic of the Snowy Mountains. A ‘natural flow scaling’ approach is applied, and the continuous daily releases aim to support ecological processes in the Snowy River below Jindabyne Dam and maintain a healthy river that is much smaller than the natural channel that existed before the river was regulated.

Following a wet year in 2021-22, water availability for the environment will again allow for a large number of high-flow releases in 2022-23, which will aim to improve ecological conditions and build additional resilience into the system. The flow pattern

is similar to previous years and mimics a snowmelt river, with greater flows during winter and spring. Five high-flow releases are scheduled between May and November 2022 to move sediment and improve in-stream habitat for native fish, platypus, frogs and waterbugs. The largest release is planned for October 2022. It has a target peak flow rate equivalent to 5,000 ML per day, which will be held for about eight hours to flush fine sediment and wet high benches and backwaters. Other peak flows will mimic winter rainfall and spring snowmelt events. Moderate-to-high flow rates will be sustained from the end of May to December 2022 to mix water in the estuary to benefit plants and fish (such as Australian bass). Lower flow rates will be maintained from January until the end of the water year in April 2023.

For further information, visit the NSW Department of Planning and Environment’s Water for the environment website at https://www.environment.nsw.gov.au/topics/water/water-for-the-environment/snowy-and-montane.

Engagement

The NSW Government is responsible for planning environmental flow releases in the Snowy River and consults the Victorian Government about the planned releases.

In 2018, the Snowy Advisory Committee will be formed. Its members will represent Aboriginal, local community and environmental interests, alongside relevant NSW and Victorian government agencies. The role of the Snowy Advisory Committee will be to provide community and expert input about the pattern of environmental flow releases to the Snowy River and Snowy montane rivers, to ensure their ongoing health.

Page last updated: 01/07/22