Holiday makers and daytrippers are being warned not to swim at Tullaroop Reservoir, near Newstead, and Hepburn Lagoon with blue-green algae detected in the waterways.
Goulburn-Murray Water issued the warning after monitoring detected high levels of blue-green algae.
Warning signs have been placed at the recreational areas but they remain open to the public. Visitors to Tullaroop Reservoir and Hepburn Lagoon can still do activities that do not involve direct contact with the water.
Blue-green algae is a naturally-occurring bacteria that grows in hot weather. It contains toxins that are harmful to humans and animals and can result in skin rashes, itchiness, asthma, numb of lips and limbs, nausea, vomiting, diarrhoea and sore eyes, ears and nose.
Other Goulburn Murray Water controlled-waterways near Bendigo, including Lake Eppalock, Laanecoorie reservoir and Cairn Curran Reservoir have no current blue-green algae warnings.
For up to date information about the current blue-green algae warnings visit https://www.gmwater.com.au/news/bga