Warragamba Dam could spill as Sydney forecast to be hit with days of rain

The water authority has warned that forecast days of continuous rain could cause Australia’s largest dam to spill.

Australia’s biggest dam is likely to spill over in the next few days, with Sydneysiders warned to brace for three days of continuous rain.

WaterNSW issued the alert on Wednesday afternoon, with the dam at 97.8 per cent capacity.

“Based on the most likely bureau forecast of 35mm of rain across the catchment over a 48-hour period, Warragamba could experience a spill,” a WaterNSW statement said.

“Under the less likely, higher-end bureau forecast of 75mm in 48 hours, the dam would experience a more significant spill.”

Sydney’s Warragamba Dam could spill in the coming days, with multiple days of persistent rainfall likely. Picture: NCA NewsWire / Gaye Gerard

In the event of a spill, this will be the third occurrence since April. Woronora, Nepean and Tallowa dams across Greater Sydney are also at risk of flowing over in the coming days.

“The community should continue to monitor advice on river levels and any flood warnings from the Bureau of Meteorology,” the statement said.

Rain is expected to develop across Sydney from Wednesday afternoon and evening, with a chance of a thunderstorm.

Up to 20mm of rainfall could hit on Thursday, with the bureau forecasting a temperature range between 12C to 19C.

The chance of rain remains high on Friday and Saturday.

Across the state, a severe weather warning for heavy rainfall has been issued for the Illawarra and parts of the South Coast, Central Tablelands and Southern Tablelands forecast districts for Thursday morning.

The bureau said a “strengthening humid southeasterly flow” could bring six-hourly rainfall totals between 50mm and 90mm, with isolated bursts of 120mm on windward ranges.

The rain is expected to ease on Friday morning; however, there is “uncertainty in the longer term movement and development of the system”.