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Water Today Title April 16, 2024

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Update 2016/12/15
Hydrology

TAKING STOCK OF THE WORLD'S LAKES

McGill University geographers have compiled the most complete global database of lakes to date. Their research, published in Nature Communications, promises to help scientists better understand the important role of lakes in the Earth's complex environmental systems – from the hydrological cycle and weather patterns, to the transport, distribution or storage of pollutants and nutrients through the landscape.

While there are plenty of measurements for lakes in some regions of the world, significant gaps have remained in the global data, such as an estimate of amount of water stored beneath a lake's surface.

"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."

Taking advantage of the latest improvements in satellite data providing precise measurements of land surface elevation, the McGill researchers related the slopes found around lakes with thousands of existing lake-depth records, confirming a longheld theory that lakes in hilly or mountainous regions tend to be deeper. Based on this, they calculated the volume of water stored in more than 1.4 million lakes that are larger than 10 hectares, or roughly 14 soccer fields. The grand total: more than 180,000 cubic kilometres.

There are more than seven million kilometres of total lake shorelines on Earth, the researchers estimate. That's about 10 times the distance to the moon and back. Lakes are constantly formed and filled over long time scales through geological and natural environmental processes, so the lake distribution on Earth today represents a snapshot of a steadily changing pattern.

The world's 10 largest lakes contain about 85% of the Earth's lake water. The remaining 15% is sprinkled across more than 1.4 million lakes – most of them in Canada. With nearly 900,000 lakes covering more than 10 hectares, Canada accounts for 62% of the world's total -- a legacy of glaciers' scouring action and their subsequent melting at the end of the last glacial period, about 10,000 years ago.

The McGill team is making its new database available for use by researchers around the world.

Q&A Dr. Bernhard Lehner

WaterToday - Can you tell us a little bit about what you do?

Lehner - I am a hydrologist who studies very large river basins or the entire water resources of the world, and I am interested to see how global change, be it through climate change or environmental changes, affects those water resources.

WaterToday - There is an impressive list of projects in this research and i would like to address the most recent project, HydroSHEDS. Is that how much water there is in every body of water, or is it how much water there is everywhere except oceans?

Lehner - Yes, there are many projects that I conducted, and the names may be a little confusing. The latest is HydroLAKES, in which we created a database that tells us how many lakes there are, how large they are (in terms of surface area), how deep they are, how much water they contain, and how old that water might be in average. We also created other databases (for example HydroSHEDS), which provide similar data for all the rivers of the world and all wetlands. We are now combining all this data to get a better idea of how the many water bodies work together.

WaterToday - How did McGill University come about doing this compilation of data?

Lehner - As a global hydrologist and researcher, I realized quite long ago that one of our biggest problem is that we don't have good enough data to use in our computer models, so I started more than a decade ago to specialize in creating these types of data sources that are used by many computer modelers today, including myself. I also have a lab with students who help me, and colleagues and collaborators, so I am not all on my own.

WaterToday - Can you tell us, if ytour hydroLAKES project is aimed at hydro electric companies? or is it for a more generic use?

Lehner - It is for generic use: everyone interested can use it. The data is free and anyone can download it. Electric companies may have some interest as well as our data also contains hydroelectric reservoirs. But we did not provide any special information about those in this project (we have another project exclusively on reservoirs though).

WaterToday - Can this work you do be useful as a climate change predictor?

Lehner - Our databases are indeed used in climate change research as the water cycle plays a big role for climate, and lakes (or rivers) play a big role for the water cycle. So it is all connected, and the better the information on lakes, the better the climate models can predict what may happen with future climate.

WaterToday - The contaminant fate research you have on your site is incredible. Given that pollution is not slowing down in our lakes and rivers, how does this information get applied. Is it to figure out which country or county is polluting the most?

Lehner - Our fate research is rather new, and it is one reason why we created the lake database (as the fate of pollution in rivers typically changes once the water flows into a lake). Our current goal is to simply understand where many substances that get into our waterways might end up, where there might be particularly high concentrations (and risks), etc. Our studies focus on detecting critical areas in the world where particularly large problems might exist. Then other researchers should go there and start measuring and apply more detailed studies to figure out what is really going on.

WaterToday - Is this information available in a simpler form for use in elementary schools in Canada? Is there someone in your offices that can speak to kids about this research? it is after all, going to be their inheritance, I would think its almost more relevant to them.

Lehner - Our data and results are currently prepared for researchers and university students, so it may be a little difficult to showcase it in elementary schools (although a nice lake map is always interesting). I agree that younger generations should be even more interested in keeping our lakes safe and healthy, so I hope that students are the right audience to put this information to good use in the future.



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