State Effort Shields Lake Tahoe from Record Runoff
A bi-state effort to reduce pollution and restore Lake Tahoe’s water clarity prevented a record amount of fine-grained sediment and other pollutants from reaching the lake’s world-famous cobalt waters in 2024, according to an annual performance report released today.
By restoring wetlands and streams, limiting dust from roads and construction sites and improving stormwater systems, partners in the Lake Tahoe Total Maximum Daily Load Program (TMDL Program) reduced fine sediment loads into the lake by 29%, and nitrogen and phosphorus inputs by 23% and 17%, compared to 2004 baseline levels. These pollutants fuel algae growth and are known to reduce Lake Tahoe's world-famous clarity and water quality.
The report by the Lahontan Regional Water Quality Control Board, which is part of the California Environmental Protection Agency, and the Nevada Division of Environmental Protection (NDEP) found that an estimated 727,000 pounds of fine sediment, more than 5,800 pounds of nitrogen and nearly 2,100 pounds of phosphorus were prevented from reaching the lake in 2024, all annual record highs since the program began tracking these statistics in 2016. The mass equivalent of fine sediment reduced would fill approximately 29 dump trucks.
“Through long-term investments in science, we’ve been able to protect one of our most treasured natural landmarks,” said Yana Garcia, California Secretary for Environmental Protection. “California is helping to stop hundreds of thousands of pounds of harmful runoff from entering Lake Tahoe each year with successful local and regional partnerships, and strong collaboration with the state of Nevada. As climate challenges grow, we remain firmly committed to restoring the lake’s clarity and strengthening its resilience for years to come.”
Results from the bi-state report found that each of the program’s urban implementing partners, the California Department of Transportation, Nevada Department of Transportation, El Dorado County, Placer County, Douglas County, Washoe County and the city of South Lake Tahoe, exceeded their pollutant reduction targets. Results are estimated using the Pollutant Load Reduction Model, therefore actual load reductions may differ.
“Protecting Lake Tahoe’s iconic clarity requires long-term commitment, collaboration and innovation,” said Jason Kuchnicki, chief of the Nevada Division of Environmental Protection’s Bureau of Water Quality Planning. “These results reflect the strength of the bi-state partnership and the dedication of local agencies implementing proven, science-based strategies to reduce pollution at its source. As we continue adapting to new challenges, this program remains a cornerstone of our efforts to safeguard one of Nevada’s—and the nation’s—most treasured natural resources.”
Launched in 2011, TMDL Program is a bi-state effort between California and Nevada to restore and enhance the lake’s water clarity to historic levels by requiring local governments and highway departments on both sides of the lake to implement measures that help prevent clarity-harming pollutants from reaching the lake. The TMDL Program awards credits to implementation partners by tracking pollution, and it allows implementers to use customized strategies for holistic pollution reduction rather than having to take a one-size-fits-all approach.
These measures, such as street sweeping and stormwater infiltration, are important steps toward achieving water clarity of at least 78 feet visibility by the end of 2031. In time, the goal is for people to once again be able to see to depths of 100 feet.
Despite the record amount of pollution reduction recorded last year, the lake’s annual average clarity in 2024 was only 62 feet deep, shallower than clarity levels in 2023 and 2022 of 72 and 68 feet deep, respectively. However, long-term trends in clarity are regarded as a more representative metric of lake health than year-to-year variation. Recent data show that the lake’s long-term clarity is not trending worse or improving.
Partners in the TMDL Program kept record amounts of fine sediment, phosphorous and nitrogen out of Lake Tahoe in 2024, according to a new California-Nevada report.
“The 2024 results show that our strategies are working, even as conditions in and around the lake become more unpredictable because of increasing pressures from climate extremes, wildfire and ecological change,” said Ben Letton, Lahontan Water Board executive officer. “Building resilience into our pollutant control efforts is essential.”
On the research front, program partners are accelerating efforts to understand the full range of complex interactions and processes that harm lake clarity, such as wildfires, warming air and water temperatures, extreme weather and invasive species. While there is uncertainty surrounding in-lake processes, scientists and agencies agree that the TMDL Program and associated pollutant reductions are fundamental to protecting the lake.
California and Nevada are working with the Tahoe Science Advisory Council to better understand additional influences on clarity. The council is holding workshops and other discussions and expects to release a report near the end of the year. TMDL agencies will incorporate the council’s findings in their yearly Findings and Recommendations Memo.
To learn more about ongoing efforts and to view the detailed 2025 performance report, please visit the Lake Clarity Tracker – Program Management page.