State of the Lake report shows extreme highs and lows of the basin, 2023 on track to follow in historic data

Pollen observed in Lake Tahoe from an aerial view.
Provided/Tahoe Environmental Research Center

TAHOE CITY, Calif.— The 2023 Tahoe State of the Lake report was released for public viewing, and Tahoe Environmental Research Center Director Geoffrey Schladow was able to present the findings at the Granlibakken Thursday, July 20. 

The report informs non-scientists about the important factors impacting the health of the basin, and provides the scientific details for preservation and management within Lake Tahoe. 

The 2023 report summarizes data collected during 2022 in the context of the long-term record of research done in Lake Tahoe. Researchers at UC Davis have been continuously monitoring the lake since 1968.

Although the report covers the data of 2022, Schladow started off the presentation by diving into data from 2023, which showed that Lake Tahoe has experienced some extreme weather events. 

“July Fourth this year was a special day,” said Schladow. “Nothing to celebrate. Fourth of July 2023 was the hottest day on Earth in a hundred-thousand years. It’s hard to get your head around that.” 

Schladow noted that temperatures are rising all around the world. 

“The climate change doesn’t just mean it’s getting warmer,” said Schladow. “These are extreme temperatures. Many of you who live up here know that we just had an extreme event. It was called winter.” 

The epic winter of 2022-23 saw the greatest amount of snow water content in the Sierra Nevadas since satellite record began in 2000. 

The northern Sierra was at 271% of its normal snowpack, the central Sierra was at 284%, and the southern Sierra was at 439% its normal pack. 

“That’s a lot of snow,” said Schladow. 

As a result, the lake level increased by over 6 feet, raising the question of what next season will bring. 

The 2022 data that was presented showed that 2022 was arguably the most extreme year for Lake Tahoe, but not from a climate perspective. 

“In other ways, it was probably the most extreme and most divergent year I’ve experienced,” said Schladow. 

Interestingly, the lake was able to deeply mix, or “turnover” in 2022, largely due to the air temperature. Nov. 2022 was on record as the third coldest month in 110 years, and Dec. 2022 was well below the long term average. 

Schawlow explained that as the warmer water on the surface cools, it travels to the bottom of the lake, where colder water already exists, causing mixing. 

This winter, the water went all the way down to the bottom of the lake, which Schladow noted was a rare occurrence. 

“This process of mixing is critically important,” said Schladow. “This is the only way the bottom of the lake gets oxygen. If this didn’t happen, the oxygen would be zero, fish couldn’t live down there, there’d be weird chemistry happening in the sediments, nutrients would be released. That would be terrible.” 

Other topics that Schladow covered during his presentation of the State of the Lake report included the increasing number of microplastics and invasive species in the lake, as well as the polar opposite of what 2023 has been so far: a dry summer and fall. 

“Remember, last year, we were in the midst of a drought,” said Schladow. “Water levels were low.” 

As a result of low water levels and higher temperatures, the growth of algae blooms around the basin occurred. 

Multiple agencies and organizations help fund the State of the Lake report, including the California Tahoe Conservancy, the Tahoe Regional Planning Agency, the League to Save Lake Tahoe, and the Parasol Tahoe Community Foundation, among many others. 

The report is available to be in read in full online, and can be downloaded at

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