Snowy River high flows 2022—frequently asked questions

A total of 202,300 megalitres of environmental water will be released to the Snowy River below Jindabyne Dam during the 2022–23 water year. During the year, the water will be released under nine separate high-flow events. The daily flow for each of these events will be above 2,000 megalitres per day and occur between 31 May and 9 December 2022. This will include five eight-hour peaks above 3,715 megalitres per day. No flow will be over 5,000 megalitres per day.

There is no flushing flow in the current 2022 schedule. Consideration is being given towards the inclusion of a flushing flow in October but is dependent on climatic conditions. An update will be provided if the schedule is varied.

The long term aim of Snowy environmental flows is to restore the river below Jindabyne Dam by scouring a smaller channel with a rocky or gravel base, better supplying pools and riffles (water running quickly over gravel beds) with fresh oxygenated water and reconnecting the river.

The flow pattern is designed to better mimic the natural flow characteristics that are typically seen in Snowy montane rivers. This flow pattern includes a higher degree of daily and seasonal flow variability, while still maintaining natural high-flow events in the Snowy. The nine high-flow events allow the river to re-establish stream function and improve the in-stream habitat.

Results from previous studies from the Snowy Flow Response Monitoring and Modelling Program show that most of the physical work (sediment movement and channel maintenance) in the river channel occurred within hours of the peak flow rate. This means multiple high-flow events of shorter duration work better than one longer event.

The continuation of the pattern of multiple high flows with short duration draws on the results of previous releases, which demonstrated that regular flow disturbances flush the sediment from the stream bed establishes a new, smaller channel within the former channel of the Snowy River.

Additionally, the high-flow events wet the riparian zone, promoting the establishment of aquatic and riparian vegetation and providing important habitat for water dependant animals including native fish, waterbugs, frogs and Platypus.

The environmental water release strategy attempts to mimic the natural hydrological characteristics of the Snowy River. Before the Snowy Scheme was constructed, high-flow events during winter and spring were commonplace.

Historically, the flow regime of the Snowy River at Jindabyne 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. The typically larger spring flow peaks resulted from rain-bearing weather systems in association with rapid melting of snow.

This release strategy provides for an increase in flow variability to better reflect the natural hydrology, with additional winter and spring high flows to represent winter and spring rainfall and snowmelt events.

The water will be released into the Snowy River from Lake Jindabyne and travel down the river to the estuary at Marlo, Victoria. The intent is to rework a smaller channel within the former Snowy River bed to improve instream habitat for aquatic biota. The largest event has a peak of 5,000 megalitres per day, which will be below the minor flood alert zone at all gauge locations on the Snowy River.

The rainfall, snowfall and hence the stream flow of the Snowy River varies from year to year. This variability in the timing, peak flow rates, duration and volume of events is a key characteristic of Australian rivers.

The daily flow targets differ from the 2021-22 water year as a different inflow sequence was used to generate the annual release strategy. This year there will nine high-flow events (the same as in 2021), with one autumn event, one winter event, five in spring and two in summer.

The partner governments agreed to recover from western irrigation areas a volume of environmental water for the Snowy River equivalent to 21% (212,000 megalitres) of the mean annual natural flows below Jindabyne Dam. The amount of water available each year is subject to the amount of rainfall, snowmelt and inflows into the southern Murray-Darling Basin storage dams.

With wetter conditions and stronger inflows across the southern Murray-Darling Basin this year, the allocation is similar to that of 2021.

^{Note: The peak flow releases will occur during daytime hours from 8am to 4pm Australian Eastern Standard Time. The release date for these flow peaks could change as they are weather-dependent.}

^{The releases to the Snowy River will be above 2,000 megalitres per day for 14 days across the nine high-flow events. In September and October there are multiple day high-flow events that will have flows larger than 2,000 megalitres per day to maximise the ecological benefits for the river.}

^{Although there is no flushing flow in the current 2022 schedule, this will be reviewed dependant on climatic conditions.}

The maximum annual flow volume is dependent on both the weather and annual water determinations in the southern connected Murray–Darling Basin, therefore peak flow releases will vary from year to year. In some years they may be higher or lower than the peak flow rates used to date. The peak will naturally reduce as it progresses downstream, but could still be detected near the mouth of the Snowy River at Jarrahmond in Victoria.

We anticipate that during the largest of the spring 2022 events on 12 October, the river level will rise from 1.10 metres to approximately 1.54 metres at the Dalgety gauge. 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 slightly greater than elsewhere.

The NSW Government recommends that equipment should be secured or elevated three metres higher than the existing base water level in the Snowy River.

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. The township of Dalgety and the Snowy River at Jacks Lookout have suitable viewing locations.

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 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.

Landholders are advised to take all necessary precautions with their stock and property, both before and during the flows.

The NSW Department of Planning and Environment, along with Snowy Hydro Limited, will continue to monitor flow conditions—both the storage releases and any natural downstream inflows occurring at this time.