Low inflows cause change to Snowy River flushing flows

Media release | 25 September 2018

Lower than predicted inflows into Jindabyne Dam as a result of the prolonged dry conditions have impacted on the ability to deliver the planned largest environmental water release into the Snowy River this year, NSW Department of Industry, Director Water Science Lynn Tamsitt said today.

“The initial planned flushing flow would have seen water released over the dam spillway, in order to achieve the desired flow rate into the Snowy River,” Ms Tamsitt said.

“Inflows into Jindabyne Dam in recent months have been less than anticipated, and the Bureau of Meteorology is forecasting below average rainfall to continue at least into December, which means the water level in the dam is likely to be insufficient to release water over the spillway.

“While using the spillway for the flushing flow is not possible, there is sufficient water within the dam to achieve similar positive environmental outcomes for the 17 October event by modifying the duration of the water released from the dam on that day through the cone valves infrastructure.”

Ms Tamsitt said the initial planned flow rate of 8,620 megalitres per day (ML/d) over an eight hour period would be replaced with a flow rate of 5,000 ML/d over a 24 hour period, occurring between 8.00am on Wednesday 17 October and 8.00am Thursday 18 October, before dropping back to 1,996 megalitres per day for the remainder of Thursday.

“The revised flow rate is expected to see the river water level at Dalgety rise from 1.05m to 1.54m, an increase of 0.49m, which is 0.3m less than the previous planned rise.

“It is important to note that water released at Jindabyne will take about five to six hours to reach Dalgety Weir at this flow rate.

“Landholders downstream of the Jindabyne Dam are advised to note the revised flow rates and longer duration of this event and take all necessary precautions with stock, fencing and property in proximity to the river,” said Ms Tamsitt.

The environmental changes from this release are expected to be greatest between the dam wall to the junction with the Delegate River. However, the pulse will be noticeable down to the estuary in Victoria.

The remaining planned high-flow releases into the Snowy River are:

  • Wednesday 3 October – equivalent peak flow 2,720 ML/d for eight hours (no change)
  • Wednesday 17 October – equivalent peak flow 5,000 ML/d for 24 hours (largest flow - changed)
  • Wednesday 31 October – equivalent peak flow 2,140 ML/d for eight hours (no change)

Environmental water releases to the Snowy River are mandated under the Snowy Water Inquiry Outcomes Implementation Deed 2002, a tri-government agreement between the Australian, New South Wales and Victorian Governments, to achieve improvements in Snowy River health.

Further information about the Snowy River environmental releases is available on the department’s website.