After a rainfall, take caution when playing in the water

A kiteboarder makes the most of a sunny day earlier this summer. PHOTO: Sophie Sutcliffe

When it comes to engaging in recreational water activities this summer, experts are saying give it time. Especially after a rainfall.

Toronto Public Health advises that people should generally wait anywhere from 12 to 48 hours after a rainfall before heading into the water.

“Rainfall does have an impact on beach water quality,” explained Mahesh Patel, Toronto Public Health’s healthy environments manager. “However, water quality is affected less during a wet summer (like we are experiencing this year), compared with a dryer summer with intermittent rainfall.”

Patel said the reason for this is that during a wet summer, contaminants are more readily washed away compared to drier summers which often cause “a greater concentration of accumulated contaminates which can enter the lake after a rainfall.”

And while residents can take some solace knowing that the heavy rain we’ve experienced this season should help to carry away contaminants in the water, Krystyn Tully, president of Lake Ontario Waterkeepers, also cautioned residents about the quality of the water and said that while the city tests the water for e coli every day, the results can take up to 24 hours. Meaning there can be a bit of a lag when it comes to getting accurate information.

Tully agreed with Patel and said the water quality is most at risk after rain, but suggested it could take even longer than 36 hours for the water to become safe place for activity again.

“The number one concern for water quality after rain is bacteria pollution,” said Tully. “When there’s heavy rain, when the sewage flows into the lake, you get this shot of bacteria pollution that comes with the sewage and then the rain subsides and the weather clears up, and that shot of sewage pollution stops, it takes about about 48 hours for the bacteria to die off,” she said.

But an even bigger issue are pools of stagnant water — several of which can be found on the beaches of Ashbridges Bay.

“We tell people to avoid stagnant water because it doesn’t move, there’s no way for it to flow or to be cleansed. So you tend to get bacteria, algae, even just the accumulation or run-on from the road, it’s going to all sit in that one place and not go anywhere,” said Tully. “[If people are] going in the water, they should be in the open lake where there is a constant movement and flow and recharge.”


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