Updated: Blue-green algae and GRCA reservoirs

Warm weather in late summer and early fall creates the perfect conditions for algae to grow and bloom in large bodies of water like the Grand River Conservation Authority’s (GRCA) Belwood Lake, Conestogo Lake, Guelph Lake, and Woolwich reservoirs.

The presence of blue-green algae has been observed at the Belwood Lake, Conestogo Lake, Guelph Lake and Woolwich reservoirs. Signage has been posted notifying the public of the conditions and the Ministry of the Environment, Conservation and Parks and the Wellington-Dufferin-Guelph Public Health Unit have been notified.

Please be aware that when blue-green algae are visible, the following precautions should be taken:

• Keep children and pets away from the algae.
• Avoid contact with the algae.
• Don’t eat fish from the lake.
• Don’t use the water for drinking or any other purpose.
• Boating is allowed, where permitted, but boaters and recreational users should avoid touching the algae.
• Don’t swim in areas where you see scum, or it is accumulating along the shoreline.

Blue-green algae thrive on nutrients from fields and lawns that find their way into local waterways and reservoirs during heavy rainfall and spring melts and cause their populations to grow rapidly, forming blooms or scum on the surface of the water. Some varieties of blue-green algae can produce toxins that are harmful to both people and pets.

When an algal bloom starts to grow, a noticeable green or brown scum will form on the surface of water bodies and the water look like green or bluish-green pea soup. Once blue-green algae are in full bloom, it may look like spilled ‘paint’ along the shoreline. A new blue-green algal bloom often smells like fresh cut grass, while an older bloom can smell like rotting garbage.

More information about blue-green algae

• Visit the GRCA website at https://www.grandriver.ca/en/our-watershed/Algae.aspx to learn more about blue-green algae on GRCA reservoirs.
• Visit the Ministry of the Environment, Conservation and Parks website to learn more about blue-green algae.

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Media Contacts:

James Clark, Senior Communications and Marketing Advisor
Phone 519-621-2763 x2240  |  Email jclark@grandriver.ca

Lisa Stocco, GRCA Manager, Strategic Communications and Environmental Education
Phone 519-621-2763 x2316  |  Email lstocco@grandriver.ca