Lake Tahoe is so blue not because it is clear. It's the algal concentration that determines the color of water
For a long time, it has been firmly believed that Lake Tahoe’s iconic blue tint is due to its clarity. But a recent study at University of California suggests this is not the case. The blueness comes from the amount of algae in the water instead of clarity. “The lower the algal concentration, the bluer the lake.”
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A postdoctoral researcher from University of California, Davis, Shohei Watanabe came up with those findings when a Blueness Index had been created by using NASA-JPL research buoy and Lake Tahoe’s color had been quantified for the first time. The results were exactly opposite to what was commonly perceived. Surprisingly no connection was found between clarity and blueness.
The research showed the blueness of the water does not remain consistent throughout the year. There were times when the lake was clearer, it was less blue and when lake was less clear, it was deep blue. The process is due to the combination of sediments, nutrients and algal production which changes with the season.
Clarity is linked with sediment while blueness is controlled by algal concentration. The less nutrient means less production of algal. Thus, more blue color of water.
“This does not mean that clarity should be dismissed,” said Watanabe. “Rather, it shows that algae concentrations and nutrient input should be managed more closely to truly keep Tahoe blue and clear.”
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Geoffrey Schladow, the director of Tahoe Environmental Research Center at UC Davis declares these findings a remarkable achievement in terms of better understand how Lake Tahoe works. “It reinforces the importance of controlling nutrient inputs to the lake, whether from the forest, the surrounding lawns or even from the air.”