What’s driving high water levels in Lake Ontario?

At the Cathedral Bluffs Yacht Club, the docks are virtually hidden thanks to the high water levels of Lake Ontario.

The sight is reminiscent of two years ago, when the lake broke water level records in what yacht club members called a “once-in-a-lifetime” event.

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But the highest it reached in 2017 was 75.69 metres, according to data from the U.S. Army Corps of Engineers.

In July 2019, water levels haven’t dipped below 75.75 metres. The average water level so far in July is 75.82 metres.

Why are water levels high this year?

Water levels are dependent on many things, but heavy rainfall is one of the main components to why Lake Ontario has seen higher levels this season.

The heavy rain can be either near the lake itself or near its inflows — the rivers and streams that feed into the lake.

“Inflows into the Lake Ontario system have been extremely high this year, due to precipitation and snowmelt in the Lake Ontario-St. Lawrence basin,” Kevin Bunch, spokesperson for the International Joint Commission, told Global News.

He also said there were high inflows from Lake Erie and the upper lakes, and heavy freshet in the Ottawa River, “which led to flooding in Montreal and restricted how much water we could let through the Moses-Saunders dam.”

All of these contribute to the record highs seen on the lake.

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Climate change and human impact

There are two main factors that are driving elevated water levels in lakes, explained Blair Feltmate, head of the Intact Centre on Climate Adaptation and professor at the University of Waterloo.

“We’re getting more storms of greater volumes of water coming down over shorter periods of time… and we’ve removed over the course of the last 100 years about 73 per cent of the natural infrastructure that was originally here,” he said.

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While the former can be explained by a changing climate, the latter is due to humans turning lands that used to be forest, fields and wetlands into paved areas or farmland.

Both pavement and agriculture development are less permeable.

“In either case, when water hits these areas of development it doesn’t absorb quickly into the groundwater system or stay on the land for long periods of time,” Feltmate said.

That means more water is running off into the rivers and streams that feed into Lake Ontario.

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Will it stay this high for years to come?

“Canada is going to become wetter going forward due to climate change,” Feltmate explained, noting that Eastern Canada and the Great Lakes regions will be hit the hardest.

That means many are asking, “Is this the new normal?”

While extreme weather is more common today than it was in the past because of climate change, Canadians’ “normal” will continue to evolve and change over the coming years — and Feltmate says it’s going to get worse.

“What’s normal today is not what was normal 25 years ago, and what’s normal 25 years from now will be beyond the extremes of weather we’re experiencing today,” he said.

“We’re not going backwards on climate change. Climate change has happened is happening and will continue to happen and we need to better prepare for high water levels and flooding.”

—With files from Kamil Karamali