Spring rainfall prompts potential Mount Bold release

SA Water is expecting to safely facilitate a controlled flow of water from its Mount Bold Reservoir in coming days, after an extremely wet start to spring delivered a further 13 billion litres of water to the storage.

So far during spring, South Australia’s reservoirs have already received more than two-thirds the amount of inflows compared to winter, with Mount Bold’s water level increasing by around 27 per cent in this time.

SA Water’s Senior Manager of Wastewater Expertise and Environment James Crocker said the utility’s comprehensive dam management procedures guide the important activity.

“The release of water is a vital measure in safely managing water levels in the reservoir and we’re keeping an eye on forecast rainfall and inflows to guide the trigger point for a release, which may include partially opening the dam’s gates,” James said.

“Mount Bold has experienced a significant rise in its storage level since the start of spring and with it now sitting at 94 per cent capacity, we’re expecting to make controlled releases of water once we reach 94.48 per cent.

“Should gates be opened, visitors will be able to see them from the Razorback Road lookout, and people may notice a small increase to the Onkaparinga River’s level, which is also fed by numerous creeks below the dam.

“Gradually releasing water at this stage maintains some air space to manage inflows, but if we receive further heavy rainfall that exceed the dam’s capacity, water releases will match natural inflows and raise the river in the same way that would happen if the dam didn’t exist.

“A number of our other reservoirs are also quite full after persistent spring rain and are either nearing, or at the point, where they are safely releasing water, such as our Kangaroo Creek, Myponga and Warren reservoirs.

“Pleasingly, our reservoirs have enjoyed a wet couple of months and are sitting at a comfortable position holding a collective 87 per cent of their capacity as we head into the warmer months.”

Mount Bold’s water release gates were last opened in August 2017, when the storage doubled its capacity in just over a month after sustained inflows to the reservoir.

Mr Crocker said while Mount Bold’s dam was not built for flood mitigation, an upcoming major safety upgrade project will now also incorporate a small amount of new flood attenuation capacity for the future.

“During the past 20 years, we’ve been working to enhance the safety of our dams and keep them in step with ever-evolving standards, with designs, planning and preliminary work underway for Mount Bold,” James said.

“When constructed in 1938, the dam was built only for water storage to support Adelaide’s population. As part of our upgrade, the State and Federal Government are providing additional funding to include improved flood attenuation measures, delivering extra protection for downstream residents for the first time.”

Preparation for the dam’s upgrade has been underway since 2010, with major construction expected to start in coming years and take several years to complete.

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