Wyangala Dam cut Lachlan flood impact by three-quarters

Wyangala Dam cut Lachlan flood impact by three-quarters

31 August 2021

Strategically timed pre-releases and round-the-clock storage management by on-site dam personnel resulted in Wyangala Dam reducing downstream impacts in the Lachlan valley from the most recent rain event by three-quarters.

With the storage reduced to 94% by weeks of pre-releases, Wyangala Dam was able to capture and hold inflows that peaked at a rate of 90 gigalitres per day (GL/day) while making dam releases no higher than 22 GL/day.

This reduced the potential peak downstream by 76%, with the rain generating a total of 170 GL of inflows into the dam storage and more than 50 GL from the tributaries downstream of the dam.

Wyangala Dam personnel were in 24-hour flood operations from Wednesday (25 August) to Saturday (28 August) to monitor inflows following rainfall that averaged about 55mm over the catchment.

WaterNSW will reduce releases from Wyangala as downstream flows in the Lachlan River peak, after consulting with the Lachlan valley airspace reference panel yesterday (Monday).

Dam releases will be reduced from 20 gigalitres per day (GL/day) to 14 GL/day, a rate at which storage airspace will be maintained but that will allow downstream river heights time to drop at locations such as Nanami, Forbes and Jemalong Weir.

Wyangala Dam is currently at 98.6% of capacity and holding 1200 gigalitres with the Bureau of Meteorology forecasting a small rainfall event for the weekend. The rate of dam releases will be adjusted to accommodate any significant change in that weather forecast.

With the Bureau of Meteorology continuing to forecast a climate outlook that “indicates rainfall over the coming three months likely to be above average”, WaterNSW will continue to make airspace releases as required to manage storage levels in consultation with Lachlan airspace reference panel.

WaterNSW will continue to work in conjunction with and consult local advisory panels, comprised of landholders, local councils, the NSW State Emergency Service and other key stakeholders.

Agency

Information

Website

Bureau of Meteorology (BOM)

Weather forecasts and warnings

BOM

NSW State Emergency Service (SES)

Flooding and severe weather warnings and advice

NSW SES

Media contact – Tony Webber 0428 613 478

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94.0
Tuesday 19 October
0.2
2,426,378 ML
2,581,850 ML
9,092 ML
1,299 ML
4,444 ML
Tuesday 19 October