The purpose of the winter drawdown is to control the extensive build-up of the highly invasive aquatic weed, which can displace submersed native vegetation and impacts on the lakes’ usage, making it harder to swim, fish, launch boats and water ski.
Previous winter drawdowns have proven effective in controlling the weed, which dies off as it dries out and is exposed to frost.
The last drawdown was in 2022 when the lake was lowered by five metres.
A spokesperson for Goulburn Murray Water said the decision to keep the water level at full supply over the 2026 winter period came after a survey to gauge weed growth, which found that levels of growth were acceptable.
“The decision was also made given there are no major works planned on the structure this year requiring the lake to be lowered,” they said.
With levels of Egeria weed noticeably increasing in the lake, coupled with recent extreme temperatures, some locals have questioned whether there is a heightened risk of blue-green algae.
Goulburn Murray Water, which issues warnings when blue-green algae exceed safe levels, has advised there is no current warning for Lake Mulwala.
As blue-green algae levels can increase quickly, it is recommended the public avoid contact with any scums or discoloured water if they appear,” the spokesperson said.
“Interestingly, blue–green algae may colour the water blue, green, yellow, brown or red.”
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