Moderate Warragamba dam spill likely overnight

Based on current WaterNSW modelling, the dam could spill at a peak rate of approximately 60 gigalitres per day (GL/day).

The duration and volume of the spill will ultimately be determined by rainfall received across the catchment today.

If the forecast peak spill rate of 60GL/day is realised it will fall within the range of the most recent spill events:

• 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)

Smaller Sydney dams such as Cataract, Nepean, Cordeaux, Avon and Woronora started spilling overnight and all continue to spill. Fitzroy Falls, Tallowa, Greaves Creek and Medlow dams were already spilling, and will continue to do so.

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. This includes three times in mid 2024 and once in May 2025.

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 – 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.