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University of Melbourne researchers have developed a way to quantify the cost of maintaining a secure water supply, allowing authorities to better plan for the future and avoid costly responses to low water levels.

The report, The economic value of water in storage, makes the assumption that water authorities will build more desalination plants rather than experience a water shortage crisis like Cape Town. It estimates how different ways of operating the system affect the expected cost of maintaining water security at different levels for Melbourne over the next 20 years.

Report co-author Professor Andrew Western, from Infrastructure Engineering at the University of Melbourne, said this approach allows people to appreciate the value of water in storage at all times, not just when there is a crisis.

“Our research shows that maintaining sufficient water in storage has a significant economic value as it reduces the need to expand the water supply system, and/or delays it,” Professor Western said.

“While there is controversy surrounding the cost of desalination (the process of removing salt from seawater so it can be used to supply drinking water), we found that using the Victorian Desalination Plant for the first time last year as our storage levels fell again was the right move. Without that use, current levels would still be falling, as they have been slowly since 2014. 

“In fact, if the past four years from 2014 were repeated over the next four to 2022 and we did not use the desalination plant, we would be on, or close to, Stage 3 water restrictions and be seriously considering expanding the existing Victorian Desalination Plant.”

Co-author Nathan Taylor from the University of Melbourne said knowing when to buy additional water from a desalination plant and at what price, or when to invest in an alternative source such as rainwater harvesting, allows authorities to make more informed decisions and plan for the future.

“In the past, decisions have been made in response to severe stress,” Mr Taylor said.

“Good planning allows us the flexibility to go to somewhat lower storage levels before making the final decision to build more infrastructure.

“It took about five and a half years to design and build the Victorian desalination plant, but nearly half the project timeline involved planning, various approval and procurement processes, and land acquisition.

“We estimated that if future expansion could be undertaken in two years, the average cost of maintaining water security could be reduced by more than $100 million, given current storage levels.”

Read more on Pursuit.