Lake Tahoe, which straddles the Nevada-California state line, is famous for its clear waters.
But the lake is changing. For decades, the depth of the lake’s famed clarity has plateaued. The threat from invasive species has increased. There are fewer days below freezing, and summers are getting longer and hotter. And that doesn’t include one of the biggest threats to the area: wildfires.
That’s according to the latest “State of the Lake” report from the UC Davis Tahoe Environmental Research Center. The annual report was released on July 17, and includes data collected from the Lake Tahoe Basin during 2025.
This year’s report continues to detail the effects the warming climate is having on the jewel of the Sierra.
According to Alex Forrest, associate director, Tahoe Environmental Research Center, University of California, Davis, that shift in seasonal weather changes how much sediment ends up in the lake. That can have a dramatic impact on Tahoe's famed clarity.
"We have these organic particles in the form of these small plankton that can grow in this system, and we are now trying to understand those shifts of organic particles in the water and their impact on clarity as well, and so this is one of our new emerging areas of research," he said.
Wildfire smoke is also playing a role in the lake's health — even distant fires are having an impact.
"It deposits particles, and those particles are a combination of carbon and other inorganic components that get deposited in the lake, and then those particles are then transformed or aggregated and transported through the water," said Forrest. "We are trying to understand what those impacts are. Do they reduce light conditions? What are the impacts of the reduced light conditions? Are they a source of nutrients, and ... are they a potential source of other contaminants?"
Guest: Alex Forrest, associate director, Tahoe Environmental Research Center, University of California, Davis
