Canada has the most lakes of any country, but we know very little

Lakes are a vital part of our ecosystem, but it turns out, we take them for granted.

One hydrologist decided to change that

We canoe on them, swim in them and drink from them, but how much do we really know about the water in lakes and how important they really are? (Submitted by Pat O.)

Canada is home to the most lakes in the world, but it turns out we don't know a lot about them.

Bernhard Lehner, associate professor at McGill University's department of geography decided to change that. He produced a new global database to help scientists from around the world study the role of lakes in Earth's ecology. 

While we often focus on the lifecycle of oceans and their important roles in global terms, lakes around the world — more than a million — are also influenced by — and can influence — weather patterns, ecology and even climate.

Though scientists have plenty of tools to study lakes and waterways, including satellites, they aren't able to see too far below the surface. In fact, scientists have only been able to catalogue about a hundred lakes accurately. 

What if they start disappearing? What ecology would disappear with them if they go?- Bernhard Lehner, McGill University

Lehner, who was the database's senior author, estimated the depth and water content for 1.42 million lakes around the world. The study focused on those that are 10 hectares and larger. And of those, Canada is home to a whopping 62 per cent.

The role in Canada's ecology can't be stressed enough, he said. 

"You need to appreciate how important they are in the whole water cycle," Lehner said. "In Canada, there's no water cycle without them, really."

The Great Lakes play a vital role in the weather and climate of Ontario. (NASA image courtesy Jeff Schmaltz, MODIS Rapid Response Team at NASA GSFC.)

And, because Canada has so many lakes, we really need to take stock and pay more attention to them, he said.

"What if they start disappearing? What ecology would disappear with them if they go? What role do they play for weather and climate? Learning more about them is part of what Canada should do."

And the lakes can be highly influenced in a changing climate. In the north, which has most of the lakes in Canada, the future is uncertain: if the permafrost melts, we could lose lakes as they drain into the ground. But new lakes might also form. 

How old?

Another part of the study was calculating how long the water lasts in the lakes. 

In Ontario's Lake Superior, for instance, the water lasts about 130 years. Water in Great Bear Lake in the Northwest Territories has almost the same lifespan, between 120 and 130 years.

Map of the world's lakes with surface areas of 10 hectares or more. The large, dark blue areas in Canada reflect the high concentration of lakes in those regions. (HydroLAB, McGill University)

This new information helps scientists determine how that water might interact with the environment and life around it. For example, if a lake becomes highly polluted or heavy sediment flows into it, researchers will now be able to get a better idea about the repercussions.

Lehner hopes that this new information will help advance more knowledge and study on the world's lakes.

"We often say that we know less about the ocean floor than about the surface of Mars … and lakes, we assume we know more because they're closer to us, but that's not the case."


Nicole Mortillaro

Senior reporter, science

Based in Toronto, Nicole covers all things science for CBC News. As an amateur astronomer, Nicole can be found looking up at the night sky appreciating the marvels of our universe. She is the editor of the Journal of the Royal Astronomical Society of Canada and the author of several books. In 2021, she won the Kavli Science Journalism Award from the American Association for the Advancement of Science for a Quirks and Quarks audio special on the history and future of Black people in science. You can send her story ideas at