Hawkesbury, NSW, 20 August 2022 – Almost 300 concerned flood-affected Hawkesbury Residents converged on the Hawkesbury Race Club in Clarendon this afternoon to understand what urgent flood mitigation options might be possible if the NSW Government changed the legislation to allow Warragamba Dam to be used for flood mitigation as well as water supply.
The community and State, Federal and Local politicians, heard from UNSW's Dr Stuart Khan, a Professor in the School of Civil & Environmental Engineering and Director Australian Graduate School of Engineering (AGSE). He is widely considered one of the leading experts in water management and was able to discuss all the aspects of lowering the Full Supply Level (FSL) of Warragamba Dam.
The forum was arranged by Hawkesbury Community Alliance, an amalgamation of several local community interest groups. It is urgently calling upon the NSW Government to investigate flood mitigation options ahead of the predicted third La Nina, and Indian Ocean Dipole events predicted to coincide in Spring 2022.
"The NSW government stubbornly remains focussed on raising the dam wall, a project that 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 dam level ahead of predicted weather events. Nor do we feel the Government feels any real sense of the impending disaster," says a Hawkesbury Community Alliance Spokesperson, Samantha Magnusson.
"Our community needs flood mitigation now, not in the distant future. Ten years is too late."
She continues: "Today, Professor Khan clearly demonstrated that lowering the Warragamba Dam Full Supply Level (FSL) by 12 metres is not only possible but is the best option for urgent flood mitigation for the community, who are filled with fear and uncertainty about what a third La Nina and negative Indian Ocean Dipole weather system in coming weeks might bring. Had they used the dam for mitigation in the last flood, we would have recouped all the water from the rain event."
Professor Khan told the community "Reducing the current water storage in Warragamba Dam is a realistic alternative to raising the dam wall. While no solution provides complete protection from flooding, maintaining a lower water storage in Warragamba can significantly mitigate many floods, reducing peak flood heights and enabling additional evacuation time".
However, Professor Khan warned that reduced storage in Warragamba Dam would decrease Sydney's drinking water supply security and would only be viable if drinking water supply was immediately replaced by alternative sources:
"Any reduction in reliance on Warragamba Dam must be accompanied by the introduction of new rainfall-independent water sources, such as new seawater desalination or water recycling. In addition to enabling flood mitigation at Warragamba Dam, new rainfall-independent water sources will provide significantly enhanced drought resilience for Sydney".
The Hawkesbury Community is urgently calling on the Government to allow the Full Supply Level (FSL) of Warragamba Dam to be lowered ahead of predicted flooding to prevent a repeat of the July 2022 scenario. In that last flood, water commenced spilling over the dam wall at 2 am, without any warning to the community by Water NSW Early Warning Network. The following morning, a press release was put on the Water NSW web page. As a result, the community was caught off-guard. An unprecedented increase in water level and flow velocity resulted in a much-reduced evacuation timeline, excessive flood damage, and irreparable damage to the riverbank, all of which could have been prevented, if managed differently.
"It is essential to consider the 'big picture' for water management in Sydney, rather than look at individual components in isolation," says Khan.
