The Volume and Mean Depth of Earth's Lakes

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The Volume and Mean Depth of Earth's Lakes

With mathematical analysis, researchers have now calculated that the depth of lakes is 30% lower that it was thought so far.

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Using GPS and the depth sounder by boat takes a lot of time so scientists decided to apply the mathematical analysis.

David Seekell, at Umeå University in Sweden, and his American collaborators now believe the depth of lakes is 30% lower than what previous estimations showed.

If lakes are indeed shallower, this means there is less fresh water and this changes our approach to understanding climate change and the carbon cycle.

They estimated that the volume of lakes on Earth is around 190,000 km3. To put it in perspective – the oceans  contain 1.3 billion km3 of water.

“If we poured the water of all lakes on Earth together into one big lake, the mean depth of the lake would be 42 metres. The mean depth of the ocean is 3,682 metres,” says David Seekell.

What should possibly worry us it that if lakes are more shallow, they may release more methane that previously thought.

It is challenging to measure the volume of lakes on the global scale.

It is easy to measure the volume of large lakes but measuring small ones takes a lot of time and it should be done in the field.

The depth and coordinates of the lake have to be measured by driving in a boat and using GSP and the depth sounder. Bathymetric maps are then built based on the collected data.

The scientists decided to use a theoretical approach and assumed the Earth surface is self-affine.
Self-affinity is a feature of a fractal whose pieces are scaled by different amounts in the x- and y-directions.

“This basically means that if you zoomed in and out of a cross-section of Earth's surface, the statistical characteristics of the vertical topography are predictable based upon a stretching factor,” says Seekell.

The scientists evaluated their model by comparing their calculations to known measurements of thousands of larger lakes and it proved to be accurate so they made a theoretical volume-area relationship.

Access the research here

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