Government confirms Warragamba Dam safety and flood risks

The NSW government has confirmed today that Warragamba Dam is potentially no longer safe due to potential risks associated with extreme flooding scenarios.

The government has also revealed that the concerns were known to the previous Liberal National party government as far back as 2020 yet were kept secret –  they were only revealed in bureaucratic briefings to the new government last month.

“Under extreme and rare flooding scenarios, it is theorised that a geological seam under the dam wall could threaten its integrity, or under the most extreme scenario, water levels in the lake behind the dam could rise and cause the dam to be overtopped, which could damage the dam asset (wall and gates).” WaterNSW said in a media release.

The surprise and deeply concerning findings come less than one year after a series of five major floods devastated the Hawkesbury causing widespread damage that is still being remediated. It also follows controversy over the former Liberal National government’s plans to raise the dam wall by 14 metres.

Last June, the Hawkesbury valley experienced one of the largest floods on record, exacerbated by Warragamba dam releasing an astonishing daily equivalent of water compared to the expanse of Sydney Harbour. This catastrophic event followed four major flood incidents within the previous 18 months, during which water also spilled from the dam. 

Revelations have now come to light that WaterNSW had initially informed the regulatory body Dam Safety NSW about potential issues at Warragamba Dam three years ago, in 2020. A report today by The Guardian newspaper exposed this disclosure.

Downstream communities have been left in the dark for years about the dam’s problems.

WaterNSW confirmed today that it conducted comprehensive studies in March this year, establishing the gravity of the “climatic and geotechnical risks” confronting the dam in its current state. It said there are no immediate structural concerns with the dam wall and it does not require immediate repairs. 

However, it also said that investigations have commenced to determine the necessary measures to address the identified issues and ensure compliance with the latest safety regulations for dams in NSW.

“…They could involve the construction of a concrete buttress and/or anchoring to strengthen the current wall, however these responses are still being investigated,” it said.

Emphasizing the current safety of day-to-day operations, WaterNSW reassured the public that Warragamba Dam remains structurally sound and has the capability to withstand extremely large and rare floods. But the agency confirmed that, in collaboration with Dam Safety NSW, it is conducting an in-depth risk assessment and investigation to evaluate any required actions.

Water Minister Rose Jackson spoke to The Guardian, stating that the risks to residents in the Hawkesbury Nepean floodplain, located downstream of the dam, are deemed “infinitesimal.” 

“WaterNSW are working with Dam Safety NSW to do that really thorough risk assessment and investigation to give us any sense of what, if any, action needs to be taken,” Jackson said.

The unsettling revelations come after heated debate over plans by the Liberal National coalition to raise the dam wall by 14 metres. The unfunded project was announced during the last state election campaign and was estimated to cost between $2bln and $3 bln.

They claimed raising the wall would prevent 10,000 homes in western Sydney from flooding during a record flood and stop 70,000 residents from needing to be evacuated. Labor campaigned against the plan arguing that close to half of the tributaries responsible for flooding did not flow into the dam.

Given today’s revelations about the dam’s integrity it is unclear whether that massive project championed by the Liberal National coalition was designed to remediate the problems with the dam wall which at the time remained secret.

The Hawkesbury Post contacted Hawkesbury Council and State member Robyn Preston – who represents the Liberal Party – for comments on why the dam’s issues were not disclosed to the local community for three years – and whether they knew.

Hawkesbury City Council General Manager Elizabeth Richardson said: “Council does not currently have a position regarding the WaterNSW statement.”

Ms Preston did not respond to HP’s enquiry.

You can read WaterNSW’s statement here: https://www.waternsw.com.au/community-news/media-releases/2023/waternsw-statement-warragamba-dam