Warragamba Dam set to spill as looming “significant rain event” pushes it to capacity

WaterNSW is monitoring a significant rain event making its way into the Greater Sydney catchment, which is likely to push some Sydney dams – including Warragamba – beyond capacity and into a spill situation.

The spill – according to WaterNSW – should be below the spill experienced during the devastating March 2021 floods, but would add to already high river levels and lead to some flooding downstream. That would affect the Hawkesbury but at this stage we don’t know if we’re looking at minor or major flooding.

Heavy rain is set to hit the Hawkesbury from Wednesday morning and on into Thursday, as well as falling over Warragamba’s broad catchment area.

With Warragamba at 100% full by this afternoon, and Sydney’s overall dam network at 97% of capacity, heavy rain forecast by the Bureau of Meteorology for midweek is likely to generate sufficient inflows to cause spill events at a number of dams, says WaterNSW this afternoon – Monday.

Warragamba Dam’s spill rate is likely to be below the spill experienced in March 2021 during the major Hawkesbury flood event, but still likely to result in downstream river level increases, says WaterNSW.

“The spill rate will be determined by the intensity of the rainfall and the inflow generated.”

Tallowa and Cordeaux Dams are already spilling and other Upper Nepean storages likely to spill in the days ahead include Nepean, Avon, and Cataract, along with Woronora Dam to Sydney’s south,” says WaterNSW.

WaterNSW will be monitoring any impacts on the quality of water in dam storages as a result of the inflows, and working with Sydney Water to manage supply.

WaterNSW advises landholders and the public to monitor advice from the Bureau of Meteorology regarding changing river heights and the need for precautions with livestock and infrastructure.

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