If you walked up to the water of Lake Tahoe in 1968, you’d be able to see 108 feet down to the bottom. Today, following over 50 years of human activity on the lake, you can only see 62-feet down into the water.
The University of California, Davis Tahoe Environmental Research Center released its annual Lake Tahoe clarity report recently, showing that the water’s clarity decreased from 70.9 feet in 2018 to 62.7 feet in 2019. The sharp decline in clarity is troubling, even though its on par from recent years of clarity research.
“On its face, this data is startling, but not unexpected,” said League to Save Lake Tahoe CEO Darcie Goodman Collins in a statement. “After an encouraging 10-foot gain in clarity from 2017 to 2018, the losses from 2018 to 2019 reveal how strongly Tahoe’s blue is tied to the effects of the climate crisis and influenced by the Lake ‘turning over’ or mixing all the way to the bottom. It also spotlights the need for everyone of us — public agencies, environmental organizations, local businesses, visitors and residents — to do all we can to Keep Tahoe Blue.”
Researchers credit the decreased water clarity to numerous factors including increased precipitation in 2019, increased algae growth in the lake and warming temperatures of the lake. While the numbers are troubling, it’s best to look at the 5-year median clarity numbers in order to truly determine the rate of clarity decreases.
One marvelous clarity event that happened on the lake in 2019 was its mixing all the way to the bottom for the first time in 8 years, creating 112 feet of clarity on February 19, 2019. When mixing occurs, clean water is forced to the top, creating beautiful clarity on the lake, but creating algal blooms later in the year.
With the Covid-19 quarantine keeping most people off the lake for months on end in 2020, researchers are hopeful the lake will see improved clarity numbers in next year’s study.
Lake Tahoe has a unique location within the mountains that maintains its clarity through even the highest tourist traffic. Most of the precipitation in the area falls directly on the lake, allowing it to naturally filter the water through the nearby marshes and meadows and keeping the clean water right in the middle. While the lake’s water clarity sat at 100 feet in 1968 (meaning you could see 100 down into the water), today the lake’s clarity is only at 60 feet due to recent drought conditions and human activity on the lake.