Warragamba Dam spill forecast likely in coming days
1 JULY 2025WaterNSW is advising the public that based on current rainfall forecasts by the Bureau of Meteorology, there is a likelihood Warragamba Dam may fill and spill in coming days.
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.
The Bureau’s forecast for widespread, heavy coastal rain in coming days includes less intense falls in the Warragamba catchment. This could result in the dam filling and spilling as early as midweek under the higher-range scenario of the forecast.
Under the more likely forecast, the dam would begin to spill a much lower volume later in the week or into Saturday.
The smaller Sydney dams, including Cataract, Cordeaux, Avon, Nepean and Woronora are also likely to spill.
Fitzroy Falls, Tallowa, Greaves Creek and Medlow dams are 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.