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 this 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, Industry and Environment plans environmental flow releases 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.

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. At most, it is equivalent to 21 percent of what the average annual natural flows were 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 freshwater fish (such as river blackfish and Australian grayling). 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

While dry conditions were observed in late autumn and early winter 2020, above-average rainfall was recorded in the Snowy River catchment over late winter, shifting to average conditions over spring. Summer storms brought about by La Niña conditions resulted in very much above-average rainfall across the catchment, and a minor flood occurred

in March 2021. Water availability for environmental flows in the Snowy River is determined by allocations in the Murray, Goulburn, Loddon and Murrumbidgee rivers. In 2020-21, water availability for the Snowy River was relatively low, due to dry conditions in 2019-20. Total water allocated for environmental releases was 91,476 ML1, which was among the lowest allocations received since 2011. For comparison, 117,871 ML was released in 2019-20.

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. Relatively small peak magnitudes for high flows and shorter durations for freshening flows were delivered from Lake Jindabyne in 2020-21 because of reduced water availability. Four winter/ spring high-flow events were released (one less than in 2019-20), and a flushing flow occurred in September 2020, although it had a limited effect on the flow in Victoria. In the lower Snowy River within Victoria, several peaks over winter and again in October were observed, which was likely from a combination of the upstream environmental flow releases and contributions from major tributaries within Victoria (such as the Buchan River). Wetter conditions and consistent inflows into storages throughout the Murray-Darling Basin in 2020-21 will significantly boost allocation for Snowy River environmental releases in 2021-22.

East Gippsland CMA has monitored the lower reaches of the Snowy River and its estuary for the past nine years. Their results indicate that the managed environmental flows help improve physical and ecological processes, increase ecosystem productivity and improve 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, the prevailing conditions have provided good growing conditions for natural vegetation 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 2021-22 is 209,577 ML. This is one of the highest allocations of water for the environment made available for the Snowy River.

Due to operating rules in the system, the daily flow regime that will be delivered in 2021-22 is pre-planned: the storage manager will make daily releases of varying magnitude from Lake Jindabyne between May 2021 and April 2022 to mimic the typical flow pattern 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 several years of dry conditions, the increased water availability for the environment allows for a larger number of high-flow releases in 2021-22, with greater peak magnitudes. The flow pattern is similar to previous years and mimics a snowmelt river with higher flows during winter and spring. Nine high-flow releases are scheduled between June and November 2021. These include a large flushing flow in October 2021 that has a target peak flow rate equivalent to 10,362 ML per day, which will be held for about eight hours to flush sediment and wet high benches and backwaters. Other peak flows will mimic winter rainfall and spring snowmelt events. Collectively, the multiple high-peak flows of the planned regime aim to improve the physical attributes of the river by scouring and depositing sediment and improving in-stream habitat for native fish, platypus, frogs and waterbugs. Moderate to high flow rates will be sustained from July to December, helping to mix water in the estuary to benefit plants and fish (such as Australian bass). Lower flow rates will be maintained from December or January until the end of the water year in April 2022.

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: 22/01/21