Hawkesbury, NSW, 20 August 2022 – Almost 300 Hawkesbury residents affected by the floods converged on the Hawkesbury Race Club in Clarendon this afternoon to understand what urgent flood mitigation options could be possible should the NSW Government change the legislation to authorize the use of the Warragamba dam for flood mitigation as well as water supply.
The community and state, federal and local politicians heard from UNSW’s Dr Stuart Khan, Professor in the School of Civil and Environmental Engineering and Director of the Australian Graduate School of Engineering (AGSE). He is widely regarded as one of the leading water management experts and has been able to discuss all aspects of lowering the Full Supply Level (FSL) of the Warragamba Dam.
The forum was organized by Hawkesbury Community Alliance, an amalgamation of several local community interest groups. It urgently calls on the New South Wales government to explore flood mitigation options ahead of the predicted third La Nina and Indian Ocean Dipole events which are expected to coincide in the spring of 2022.
“The NSW Government remains stubbornly focused on raising the dam wall, a project which will take several years. Despite the damning findings of the NSW Upper House July 2022 Flood Inquiry and the Government’s response published last week, we still have no commitment to lower the level of the dam ahead of the forecast weather events. We also don’t think the government really senses the impending doom,” said Hawkesbury Community Alliance spokeswoman Samantha Magnusson.
“Our community needs flood mitigation now, not in the distant future. Ten years is too late.
She continues: “Today Professor Khan has clearly demonstrated that lowering the full supply level of the Warragamba Dam (FSL) by 12 meters is not only possible, but is the best option for urgent flood mitigation. for the community, which is filled with fear and uncertainty about what a third La Nina weather system and a negative Indian Ocean Dipole in the coming weeks could bring. mitigation during the last flood, we would have recovered all the water from the rain event.
Professor Khan told the community: “Reducing the current water storage in the Warragamba Dam is a realistic alternative to raising the dam wall. While no solution will provide complete flood protection, maintaining lower water storage in Warragamba can significantly mitigate many floods, reduce flood peaks, and allow additional evacuation time.”
However, Professor Khan warned that reducing storage in Warragamba Dam would reduce the security of Sydney’s drinking water supply and would only be viable if drinking water supplies were immediately replaced by alternative sources:
“Any reduction in reliance on the Warragamba Dam must be accompanied by the introduction of new sources of water independent of rainfall, such as new desalination of seawater or recycling of water . As well as providing flood mitigation at the Warragamba Dam, new sources of water independent of rainfall will significantly improve Sydney’s drought resistance”.
The community of Hawkesbury is urgently calling on the government to allow the Warragamba Dam’s Full Supply Level (FSL) to be lowered before the predicted flooding to avoid a repeat of the July 2022 scenario. During this latest flood , water began to overflow the dam wall at 2am, with no warning to the community by Water NSW Early Warning Network. The following morning a press release was posted on the Water NSW webpage. As a result, the community was caught off guard. An unprecedented increase in water level and flow velocity has resulted in significantly reduced evacuation time, excessive flood damage, and irreparable damage to the bank, all of which could have been avoided had they were handled differently.
“It’s essential to have an overview of water management in Sydney, rather than looking at individual components in isolation,” says Khan.
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