FOUR Wimmera lakes could be unsafe for human use, following more outbreaks of blue-green algae.
GWMWater issued an alert on Wednesday, advising algae had been detected in Taylors Lake.
Horsham Rural City Council is also monitoring a possible outbreak at Green Lake.
Earlier this month, GWMWater announced the detection of algae in Lake Lonsdale, and in February, Lake Toolondo.
Horsham Rural City Council sustainability, environment and emergency manager Rob Moir said results from water tested at Green Lake would be available on Friday.
"We are anticipating the water will test positive for algal bloom," he said.
He said while it was disappointing for recreational water users, Green Lake water quality was better than in previous years.
"If we look at this time last year, and even the year before, we were already experiencing blue-green algae," he said.
"It is good that it has been clear throughout summer."
Mr Moir said swimmers in Horsham were now limited in where they could swim.
"With the weather we've had, this was not unexpected," he said.
"We haven't had normal, sustainable summer rain, the water levels have dropped and the weather has stayed warm.
"These things happen."
Mr Moir said all Wimmera waterways were tested regularly.
He said the Wimmera River was not contaminated.
"It all depends on the weather if we could get a bit of rain that would help," he said.
Mr Moir said warning signs were already in place at Green Lake.
He said people should avoid all contact with the water.
GWMWater warns if contaminated water comes in contact with human skin it can cause skin rashes, itchiness, sore eyes, ears and nose or, if swallowed, might induce nausea and vomiting.
GWMWater spokesman Andrew Rose said blue-green algae was a common problem at this time of the year.
"We just need some rain," he said.
He said it was not possible to predict how long the algae would remain at high levels.