Melbourne Water is advising people to avoid contact with the Werribee River downstream of the Maltby bypass following the detection of blue-green algae.
Testing confirmed the presence of an algal bloom, which commonly occur in the hot, dry conditions of summer.
Melbourne Water waterways manager Cameron Howie said there were many forms of blue-green algae and the species in the river could be harmful to animals or humans.
“It’s important that people and their pets avoid contact with the water and make sure that it doesn’t come into contact with skin or eyes,” he said.
“Anyone who diverts water from the Werribee River downstream of the bypass should stop doing so while the bloom is active.”
Mr Howie said signs had been placed in the area to warn people of the potential hazards. Regular sampling of the water would continue to monitor the problem.
Melbourne Water is working with other authorities to manage the algae bloom in line with state government guidelines.
It is hoped a water release from Melton Reservoir scheduled for this week will assist by providing fresh flows to the system.
Blue-green algae occurs naturally in waterways and erupts into blooms during hot weather and periods of drought, or where there is an accumulation of nutrients in waterways or water bodies.
