Warragamba Dam spill has commenced

7 JUNE 2024

Following heavy overnight rainfall across Sydney's water supply catchments, Warragamba Dam is at full capacity and started spilling at 4.20am today.

At 7 am today Warragamba Dam was spilling at a rate of 150 gigalitres per day (GL/day) and increasing. Total inflow to the dam was 270 GL/day and rising.

The Warragamba catchment received 87mm of rain in the 48 hours to 6am Friday. The Upper Nepean catchment received 129mm rain in the same period, and the Woronora catchment 111mm.

Other Sydney dams spilling as at 7am today are Woronora, Nepean. Cataract, Cordeaux, Avon and Tallowa, and the Blue Mountains storages, except Upper Cascades.

WaterNSW continues to work with the Bureau of Meteorology and SES to monitor the weather event.

Follow the Bureau of Meteorology for flood advice and warnings and the NSW State Emergency Service as the lead agency for emergency response.


Spills from Warragamba Dam are not uncommon, occurring more than 50 times since 1960. In 2024 the dam spilled on 5 April (peak spill rate 220GL/day) and 6 May (peak spill rate 30GL/day).

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.

The gates can be manually operated to reduce the level of water in the lake for operational or maintenance reasons only outside of flood operations.

The dam gates are designed to safely pass extreme floods, much larger than the worst flood on record for the Hawkesbury-Nepean Valley.

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