Blame it on the algae: Researchers look into Lake Tahoe’s blueness

It was always assumed that the stunning blue color of Lake Tahoe was because of water clarity. Researchers however, proved this notion wrong and based the former statement on the concentration of algae within the water body. This was found after a postdoctoral researcher, Davis, Shohei Watanabe from University of California created a “blueness index”. The index helped clarify the misconception of Lake Tahoe’s blue color and clarity.

With the help of data from NASA Jet Propulsion Lab research buoy, and an instrument that captures light, the index quantified the color and measured the factors that contribute to the lake’s gloomy blue color.

Advocates for Lake Tahoe feared dust and sediment resulting from construction would affect the lake’s clarity. But the researchers found that clarity and blueness are, in fact, separate.

However, Watanabe stressed, “This does not mean that clarity should be dismissed. Rather, it shows that algae concentrations and nutrient input should be managed more closely to truly keep Tahoe blue and clear.”

The Blueness Index therefore confirms that the color depends on the algal concentration present in the lake, while the clarity is determined by the sediment. Algal levels then, are determined by the level of nutrients that are present to the algae and help in its growth.

Another reason that the researchers found for the blueness of Lake Tahoe was the droughts that the region has had to suffer. Less flow of water meant less nutrients and sediments, which eventually leads to lesser algae and thus, the blueness.

Seasonal changes also determine the flow of water through rivers and creeks, which make it stay blue-ish in color.

Geoffrey Schladow, director of Tahoe Environmental Research Center at UC Davis, described the findings as “remarkable achievement” in terms of better understanding how Lake Tahoe works.

Next time we visit the lake and pass a statement like “Look at the water, it’s so clear”, we will know the exact reason as to why we and the world is wrong.


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