BLUE-green algae levels in the Cobden dam have risen dramatically this month, prompting warnings for people to avoid all contact with the water.
Levels of the toxic anabaena algal species have risen from 19,010 cells per millilitre in December to 29,100cells/ml this month. Levels of another toxic algae, microcystis, have soared from 123 cells/ml to 13,850 cells/ml.
Corangamite Shire environment officer Belinda Bennett said both algal species were dangerous and posed a threat to people and animals.
"The algae produces toxins that pose a serious health risk to dam users," she said.
"Most common symptoms include skin irritations, nausea and vomiting, but it can also cause asthma-like symptoms and liver failure.
"We are advising the community to avoid all contact with the water, including fishing, and to please prevent pets from coming into contact with the water."
Ms Bennett said the council had notified the Department of Sustainability and Environment, Department of Human Services and Wannon Water about the rise in algae levels.
Warning signs were in place at the site, Ms Bennett said.
"Corangamite Shire will continue testing and once blue-green algae counts return to safe levels, the signs will be removed and the community will be notified," she said.
Water testing has also revealed that blue-green algae levels at the dam at the Simpson Historic Park have increased.
Although still only at a medium alert level, the results are cause for concern ? particularly if levels continue to increase.
Ms Bennett said the blue-green algae levels at Lake Bullen Merri continued to decrease, but algae was still present.
"While the Simpson and Bullen Merri levels are lower than the Cobden dam levels, the public should be aware that there are still potentially health risks for users of these waterways," she said.
Sign up for our newsletter to stay up to date.