LANSING, Mich. (Michigan News Source) – Scientists from Illinois State University and Southern Methodist University in Texas have published a recent study to answer the question: what does a healthy lake’s color look like? 

Using a sample size of 85,000 global lakes, Catherine O’Reilly, a professor in the Illinois State University Department of Geography, Geology and the Environment and co-author of the new study with SMU researcher Xiao Yang, used satellite images to reveal which color the lakes were between 2013 until 2020.    

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“No one has ever studied the color of lakes at a global scale,” Remote Sensing Hydrologist at Southern Methodist University Xiao Yang said, “There were past studies of maybe 200 lakes across the globe, but the scale we’re attempting here is much, much larger in terms of the number of lakes and also the coverage of small lakes. Even though we’re not studying every single lake on Earth, we’re trying to cover a large and representative sample of the lakes we have.”

After compiling and comparing the 5 million images, studies revealed that blue lakes were not very common around the world. 

“Only about 30% of the world’s lakes are most often blue, where blue is their most common color over that seven-year period,” O’Reilly said. Those lakes are located on only about 16% of the Earth’s surface.

While the Great Lakes region and Michigan have the conditions most conducive to blue water lakes, many are green or brown according to O’Reilly.  Of the five Great Lakes, Lake Erie has trended to be the least blue, in part because of its western basin algae blooms. 

Lakes covered by ice in the winter were two times as likely to have a blue color.  The scientists attribute it most likely to the colder temperatures delaying the growth of microscopic plants in the water. 

“And the aesthetics of these lakes…we generally want to go to lakes that have clear waters, that would be a blue-color lake,” O’Reilly said. “In some cultures, lakes are very important. They are going to be losing something that was important in their cultural landscape.”

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A possible future research project may be to continue looking at satellite data of Earth’s lakes for 30 years or more and continue to observe lake color changes.