High levels of potentially toxic blue-green algae have been found at Lake Tom Thumb and Kennington Reservoir.
As a result, the City of Greater Bendigo are advising members of the public to avoid contact with water at both lakes.
Tests undertaken at Lake Weeroona have found non-toxic levels of blue-green algae and do not pose any water quality issues.
Environmental health and local laws manager Susannah Milne said a lack of inflow and ongoing warm temperatures had created ideal conditions for algal blooms.
“Visitors to Lake Tom Thumb and Kennington Reservoir should obey the warning signs that are located at various points around the area and not swim or wade whilst the blooms are occurring,” Ms Milne said.
“Dogs and other domestic animals should also be stopped from entering the water. It is also important that visitors to the lakes keep their dogs on a lead at all times.”
She said the city would continue to closely monitor the situation.
Boating, fishing, sightseeing and other activities that do not involve direct water contact can still be enjoyed at the lakes.
However, care should be exercised when near the water and people who come into contact with the water should immediately wash affected skin in clean water.
Blue-green algae are very small and can be present in water where there are no obvious signs of a problem.
Visual inspections of the water cannot be relied on to determine the presence of high algae levels.
Most blue-green algae blooms do not last long; often disappearing after a few weeks, however, when conditions remain favourable, blooms can last longer.
It is therefore not known how long algae will remain at high levels within the lakes.
Blue-green algae occur naturally and can be dangerous to humans and animals.
Characteristic signs of algae contact are skin rashes or itchiness; sore eyes, ears and nose or, if swallowed, nausea and vomiting.