The blue-green algae alert was issued on Friday.
Warning signs will be positioned at major recreational areas around Lake Eildon and Tullaroop Reservoir and will remain in place while high levels of blue-green algae are present.
Lake Eildon and Tullaroop Reservoir (near Maryborough) will not be closed to the public.
Visitors to the lake and reservoir can still sight-see and enjoy other activities that do not involve direct contact with the water.
Blue-green algae occurs naturally in water bodies and contains toxins that are harmful to humans and animals.
Usual signs of algae contact are skin rashes or itchiness; sore eyes, ears and nose; or if swallowed, nausea or vomiting.
It is not possible to predict how long the algae will remain at high levels and G-MW will continue to monitor the situation in Lake Eildon and Tullaroop Reservoir.
A blue-green algae warning also remains current for Lake Eppalock.
The alert for Lake Eppalock has been in place since December 18.
Visitors to the lake can still sight-see and enjoy other activities at Lake Eppalock that do not involve direct contact with the water.
Keep up to date with current blue-green algae warnings at or by phoning 1800 013 357 and selecting the option for blue-green algae information.g-mwater.com.au/news/bga
Water supplied by G-MW is not suitable for human consumption without first being properly treated.
Human consumption includes showering, bathing, washing, cooking, ice-making and drinking.
For more information about blue-green algae and your health, visit or phone NURSE-ON-CALL on 1300 606 024.health.vic.gov.au