Burrinjuck releases extended as next rain event looms

Burrinjuck releases extended as next rain event looms

22 July 2021

WaterNSW is extending its airspace operations at Burrinjuck Dam to maximise storage capacity to capture inflows anticipated from rain forecast by the Bureau of Meteorology for the weekend.

Airspace releases, which have been underway at Burrinjuck dam since early July, have reduced the dam storage to 98 per cent of capacity today, with releases rising to 18 GL/day.

Those releases are planned to be reduced to minimum levels starting tomorrow (Friday) in anticipation of weekend rain and the likely increase in downstream tributary flows which are already generating high river levels.

Since 1 June Burrinjuck dam has received more than 378GL on inflows, of which 190 GL have been released.

Blowering Dam sits at 97 per cent of capacity and is making minimal releases (0.5GL/day), having received 309 GL since 1 June, of which 209 GL has been released.

WaterNSW executive manager of system operations, Adrian Langdon said based on weather forecasts from the Bureau of Meteorology WaterNSW has released 15% of total storage capacity in Murrumbidgee dams in the past seven weeks to manage storage levels.

“Strict rules govern flood mitigation pre-releases. Pre-releases can only occur within a window of high confidence that the weather forecast is accurate, usually only days from the predicted rain event.

“A rain event sufficient to warrant pre-releases is also likely to create tributary flow impacts downstream, which could be exacerbated by poorly timed dam releases.

“The other key factor is confidence that the rain event will generate sufficient inflows to replace water released for airspace. Severe droughts have clearly demonstrated the critical importance of water security to the communities and economies serviced by our major supply dams.”

Mr Langdon said to date both Murrumbidgee dams have been able to capture large inflows and hold the water back to allow for downstream tributary flows peak.

“Conventional wisdom has it that all the water in the river originates from the dam, but this overlooks the major contribution of downstream tributaries.

“Dams reduce the impact of potential flood events by capturing peak inflows, and then releasing that water gradually once uncontrolled tributary flows downstream of the dam have themselves peaked and are subsiding.

“Without Burrinjuck and Blowering to capture the extensive inflows of recent weeks from its upstream catchment the Murrumbidgee valley would already be experiencing flooding.”

For more information on WaterNSW storages visit: www.waternsw.com.au

Agency

Information

Website

Phone

Bureau of Meteorology (BOM)

Weather forecasts and warnings

BOM

varies by region

NSW State Emergency Service (SES)

Flooding and severe weather warnings and advice

NSW SES

132 500

Media contact – Tony Webber 0428 613 478.

Background

Dam management priorities:

  • Maintaining the safety of the dam (including releasing sufficient inflows to ensure the dam is not over-topped or otherwise structurally impacted).
  • Securing supply (making airspace pre-releases or operational releases only with a high degree of confidence that the water released will be replaced by inflows and thereby sustain long term water security).
  • Flood mitigation (only in circumstances that do not compromise the first two priorities, and do not aggravate the existing flood circumstances downstream of the dam where possible).

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95.4
Saturday 24 July
0.6
2,462,667 ML
2,581,850 ML
9,217 ML
1,317 ML
14,647 ML
Saturday 24 July