Declared as a ‘critical State significant infrastructure’ project, raising the dam wall would have resulted in the dam being able to hold an extra trillion litres of water and possibly reduce damage to 75%. Floodwaters coming through the catchment could be released in a controlled way, delaying and reducing the flood peak for thousands of residents.

Apparently if the dam wall was raised before the tragi March 2021 floods, the floodwaters would have peaked around 3.6 metres and 5 metres lower at Windsor and Penrith respectively.

By way of context, Warragamba Dam is located in a narrow gorge on the Warragamba River – 3.3km before it joins Nepean River. Nepean River becomes the Hawkesbury River downstream at the junction with the Gros River at Yarramundi. Collectively, the entire river is known as Nepean-Hawkesbury River.

Warragamba Dam is a water supply dam and provides around 80% of Sydney’s water supply. The dam was constructed between 1948 and 1960, and is 142 metres high and 350 metres wide across the river. It is currently not designed or operated for flood mitigation.

Over 80 dams in Australia have been raised at some point after their original construction.