EXCESSIVE levels of toxic blue-green algae have been found in the water at Lake Bullen Merri, Cobden Lake and Lake Hamilton.
The Corangamite and Southern Grampians shire councils have advised the public to avoid all contact with water at the popular summer spots, including drinking, swimming, fishing, boating, jet-skiing and the consumption of fish caught in the lake.
Pets and stock should also be prevented from drinking or coming into contact with the water.
Blue-green algae can be dangerous to humans and animals and can cause a range of adverse health effects including skin rashes and itchiness; irritation of the eyes, ears and nose; respiratory irritation and asthma-like symptoms.
The Corangamite Shire Council said the blue-green algae species blooming in Lake Bullen Merri could also cause permanent liver damage.
Southern Grampians Shire Council environmental health co-ordinator Pauline Porter said increased temperatures provided ideal conditions for the algae to bloom and the heat may lead to more blooms in the coming months.
“The algae were noticed this morning, and came about very quickly as the lake was monitored last night and there was no visible algae, which goes to show how quickly they can occur,” Ms Porter said.
It is unknown when blue-green algae concentrations will return to safe levels, but the councils will continue to monitor the blooms and notify the public through their websites when the lakes are safe for use.
As environmental conditions become more favourable, algae numbers start to increase rapidly and blooms, or scums, become easily visible on the water surface.