Minns Considers Lowering Warragamba to Prevent Flooding

The NSW Government is rethinking its water policy that may include lowering the capacity of Warragamba Dam to help mitigate the impact of future flooding for Hawkesbury residents.

“We’re looking at all potential changes – including dropping the maximum allowable level on Warragamba,” Premier Chris Minns said. “However, I can’t consider doing that until I supplement Sydney’s water supply in the meantime. So that’s not going to give us an immediate relief. It’s going to take a bit of time.”

At present, about 80% of Sydney’s drinking water comes from Warragamba Dam. The rest comes from a mix of other dams, the Hawkesbury-Nepean River and the Sydney Desalination Plant at Kurnell.

The plan is in line with the suggestions that many in the Hawkesbury have been making over the past week –  and years including the Hawkesbury Community Alliance, a community group established in the wake of earlier floods. Minns said the only timely answer for flood mitigation was to ban all new housing developments on flood-prone land.

The Premier’s comments come as the Hawkesbury begins mopping up after its seventh flood since late 2020. To date, successive governments have failed to implement any plans to help limit the impact of downstream flooding from the dam. 

The dam is not the main cause of flooding in all floods, when it spills it contributes to the magnitude of many. The debate around flood mitigation has been going on for years, yet action taken to help downstream communities protect against flooding and repair after flooding has been negligible. The NSW Water Minister Rose Jackson will meet with Hawkesbury Mayor Sarah McMahon this Friday to discuss floods. Cr Mc Mahon has continued to push the unfunded and tired concept of raising the dam wall as the primary flood mitigation solution.

Under the potential plan being considered by the government it would double the capacity of Sydney’s Kurnell Desalination plant, so it  can provide up to 15% of Sydney’s drinking water. 

Chris Minns on his visit to the Hawkesbury in August 2022 assessing flood damage with residents and the Hawkesbury Community Alliance

Minns said long-term solutions for flood mitigation would take time and considerable investment.

Jackson told ABC Radio  that if the city became less dependent on the dam’s water it could keep levels lower, provide a buffer for flood mitigation, and maintain the city’s water security.

“I think that delivers a broad range of benefits potentially and is actually less expensive than raising the dam wall,” Jackson said. The previous government’s policy to raise the dam’s wall was unfunded in the budget but would have cost about $1.6 billion on 2019 prices, had damaging environmental consequences and taken years to build. It was also revealed last year that the dam had cracks, an issue still being investigated.