Warragamba Dam storage level is currently at approximately 98% of capacity.

The timing and peak rate of a possible spill will depend on the exact timing and location of the rainfall received. The catchment upstream of Warragamba Dam is over 9,000 square kilometres in area and inflows can be received from a number of different rivers.

Under the Bureau's most likely scenario (44mm over 48 hours), forecast outflows from Warragamba Dam could peak at around 40 gigalitres a day.

This would be a similar volume to those experienced earlier this year:

• 22 August 2025 - peak spill rate of around 30GL/day
• 5 August 2025 - peak spill rate of around 15GL/day
• 3 July 2025 - peak spill rate of around 60GL/day
• 24 May 2025 - peak spill rate of around 20GL/day
• 7 June 2024 - peak spill rate of 240GL/day
• 6 May 2024 - peak spill rate of 30GL/day
• 5 April 2024 - peak spill rate of 220GL/day.

The smaller Sydney dams - including Cataract, Cordeaux, Avon, Nepean and Woronora - are also likely to spill.

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

• For the latest weather and flood information, check the Bureau website - bom.gov.au/
• For emergency information, contact the NSW SES - 132 500 or ses.nsw.gov.au

Background

Spills from Warragamba Dam are not uncommon, occurring more than 50 times since 1960. The Warragamba Dam catchment area covers 9000 sq/km and stretches across much of the Blue Mountains to Goulburn in the south, and to Lithgow in the north.

As manager of the state's major supply dams, WaterNSW operates Warragamba Dam in line with NSW Government operating rules and regulations.

These rules do not permit water being released to reduce the storage level ahead of predicted rainfall for flood mitigation purposes. This reflects the dam's critical role in supplying 80% of Sydney's drinking water.

Background - Warragamba Dam operations

During times of flood, the gates on Warragamba Dam automatically open and close based on water levels.

After rainfall has occurred and when the water rises above full supply level, the gates progressively open in sequence. As water levels begin to drop, the gates will progressively close in reverse sequence.