McGill researchers map every lake in the world

Q: How many decent-sized lakes are there in the world? Could you map every lake in the world?

A: 1.4 million lakes exist which are at least ten hectares big.
Q: Is there more ocean beachfront property on the planet or lakefront?
A: Lakefront, four times as much.
Q: Which country has the most lakes?
A: Canada, of course. But did you know that we have 879,800 of them? That’s about 63 per cent of the sum total!

These are some of cool new facts to be found in a new database created by researchers from McGill University’s Department of Geography. HydroLAKES, the most up-to-date and complete database on all of the world’s lakes, is the result of a three-year long odyssey in mapmaking, taken up with the express aim of providing the scientific community a tool to better understand the role of lakes within the global environment.

“Lakes are changing, in a changing world,” says Bernhard Lehner, associate professor in McGill’s Department of Geography, and senior author of a new study published in the journal Nature Communications. “Some are disappearing as there is less water to keep them filled, others are created or growing in regions where there is more rainfall. So we need a good inventory of the current status of lakes to understand and monitor their changes and the effects that this may have for our global environment.”

A main goal of the work was to find out how much water is held in the world’s lakes, something that had up until now not been rigorously determined. (The answer is 180,000 cubic kilometres, enough to cover the Earth’s land mass with 1.3 metres of water.)

To get these results, the team had to create a computer model to gauge each lake’s depth based on satellite data measuring land elevation, which can provide a good indication of lake depth. “We found that the depth of lakes is generally best reflected by the slope of their immediate surroundings (that is, within 100 m of the shoreline), which is in agreement with earlier studies,” say the study’s authors.

Lehner says his team was surprised to learn that about 85 per cent of the planet’s lake water is found in just ten lakes, a list which include three of the great lakes, Lake Victoria in Africa and, the largest freshwater lake in the world, Lake Baikal in Russia.

“It is often argued that we know more about the surface of the moon or Mars than the ocean floor,” Lehner says. “While lakes may be better studied in some ways than the vast ocean, there is certainly a similar lack of understanding of what exactly is going on underneath all those lake surfaces on Earth.”

The team also tracked the length of time water typically stays in each of the 1.4 million lakes, finding that on average it takes about five years for water to flow in and out of most lakes, although a small proportion – about 3,000 lakes – hold their water for 100 years or more.

Lehner says that being blessed with so many of the world’s lakes makes Canada the “prime country” to take on a stewardship role towards lake conservation, also adding that we mustn’t forget the key role that lakes have played in the genesis of our national winter sport, hockey.

Below: Mapping Lakes