Warning signs have been erected at the lake and people are being encouraged to avoid direct contact with affected lake water.
Direct contact with water affected by blue green algae can cause skin irritation, sore eyes, ears and nose. If swallowed it can cause cramps, nausea and vomiting.
Visitors to the Lake Bolac area are advised that they can still enjoy other recreational activities such as bushwalking and sightseeing.
Area Chief Ranger-Parks Victoria, Siobhan Rogan says blue-green algae is not uncommon at the lake.
“The blue-green algae blooms appear when there’s the right combination of temperatures, sunlight, stillness and nutrients.”
“While we can’t treat the algae, we’ll continue to monitor water quality and will remove warnings from the lake and our website when the bloom has naturally cleared. Given that it’s only early January, this may be some months away still.”