The NSW water minister has floated the idea of lowering Warragamba Dam's storage and supplementing it with desalinated water to reduce flood risks in Sydney's north-west.
The idea would mean a certain percentage of the dam's capacity would be kept aside for flood mitigation.
Rose Jackson said the city was 85 per cent dependent on water from the dam, and releasing water would be risky if drought conditions were to follow a discharge.
Ms Jackson told ABC Radio Sydney 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," Ms Jackson said.
Residents of the Hawkesbury in Sydney's north-west are dealing with the aftermath of the seventh flood in 18 months, reigniting debate about flood mitigation and the raising of the dam wall.
Ms Jackson said raising the wall of Warragamba Dam would have been expensive and not enough to prevent flooding.
"Raising the Warragamba Dam wall was always a white elephant," Ms Jackson said.
"For $2 billion, and probably a decade's work, I don't think the community would expect an outcome that didn't actually deliver what that community was very rightly asking for."
The former Coalition government planned to raise the wall by 14 metres, creating extra storage that would be kept empty until floodwater came into the catchment.
However, the idea was scrapped by Labor following its election last year.
An obvious option, expert says
University of Sydney water expert Professor Stuart Khan said using desalinated water was an obvious option as the plant was always meant to be expanded.
"It will be a cheaper option because a lot of the infrastructure is already there," Professor Khan said.
"We won't know what the cost is until we see a full business case … but it will be significantly less than the $2 billion we paid a decade ago for the seawater desalination plant."
Work on expanding the desalination plant to double its output has been in progress since 2017, but was paused when the drought broke in March 2020.
Professor Khan said the desalination plant can currently produce 90 gigalitres of water a year, which would cover dropping 40 per cent of the dam's capacity.
Premier Chris Minns had previously floated the idea of lowering Warragamba Dam's storage limit and supplementing it with desalinated water while in opposition in 2018.
Not raising the wall 'political', says mayor
The Hawkesbury's Liberal Mayor Sarah McMahon said ditching raising the dam wall was done to appease Greens votes.
"The Labor party do not want to upset those preference votes that they need to secure a lot of seats," Ms McMahon said.
"They would rather look at those political reasons rather than lives and livelihoods below the dam wall."
Ms McMahon also said Premier Chris Minns has not called her to discuss the issue.
Professor Khan said the state government also needed to look at up-scaling purified recycled water as another water source that could supplement the lowered Warragamba Dam capacity.
Purified recycled water is currently used in Richmond and Windsor in Sydney's Hawkesbury region.
He said recycled water would be less energy intensive than desalination, and facilities could be based in Western Sydney so water would not need to be piped in from the coast.
"The further you try and take that water west, the more difficult and the more expensive it is because you start having to tunnel under a city," Professor Khan said.
"So there is a limit to how much of our total water supply we can realistically produce through desalination."
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2024-04-09 06:29:54Z
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