Lake Tahoe, NV/CA – Lake Tahoe’s long-term clarity record is not trending worse, nor is it improving, according to the 2024 annual clarity report from the University of California, Davis’ Tahoe Environmental Research Center (TERC). The annual average clarity of Lake Tahoe through 2024 was 62 feet, which is down from last year’s average of 68 feet, but it is not statistically worse, the report notes.
From the 1960s to the 1990s, Lake Tahoe lost about a foot of clarity per year. Scientists pointed to fine sediment from erosion and polluted stormwater, and algae growth from increase nutrients as the main factors. Clarity dropped from an average of 97 feet to around 70 feet before it began to stabilize 20 years ago.
In 1969, the states of Nevada and California created the Tahoe Regional Planning Agency (TRPA) to better manage development and protect the lake. The agency unified environmental standards in the Tahoe Basin, protected sensitive wetland areas, and established a unique growth management system that capped development. In 1997, TRPA helped launch the Lake Tahoe Environmental Improvement Program, or EIP, to accelerate environmental restoration projects. Under the EIP, TRPA, the states, and more than 80 public and private organizations are actively working to restore lake clarity to its historic 97 feet. Agencies are meeting or exceeding pollutant load reduction targets set by the science-based plan to restore clarity, called the Clarity Challenge. Projects to treat stormwater and restore wetlands are so far capturing more than 500,000 pounds of fine sediment particles every year.
“Science-driven policies have underpinned Lake Tahoe’s protection for decades, and seeing lake clarity stabilize is an indicator that we are making progress,” said Julie Regan, executive director of the Tahoe Regional Planning Agency, which leads the EIP.
In 2024, the variation between summer and winter clarity followed a pattern similar to recent years. Winter clarity has been stable or improving, yet only averaged 69 feet in 2024 following an historic 92-foot average the winter prior. Summer averages are typically lower, and summer clarity in 2024 averaged just 53 feet. The trends are raising questions for researchers as to the main drivers of lake clarity. Today, the lake is warmer, more affected by wildfire and smoke, and its ecology is being impacted by aquatic invasive species. The report said future research should use new data, tools, and technologies to reexamine the nature of clarity-reducing particles. This will help reveal the extent to which biology — such as algae — and physical processes influence water clarity at Lake Tahoe.
Executive Director Regan said that while seeing lake clarity stabilize is positive, other trends and a lack of data are concerning. TRPA is working with the Tahoe Science Advisory Council to inform the best course of action.
“We will continue to work closely with the science community to understand where to direct our management efforts next.”
Media Resources
- Jeff Cowen, Tahoe Regional Planning Agency, 775-589-5278, [email protected]
- Stephanie Hampton, UC Davis Tahoe Environmental Research Center, [email protected]
- Kat Kerlin, UC Davis News and Media Relations, 530-750-9195, [email protected]
Press kit of images and figures.
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The Tahoe Regional Planning Agency leads the cooperative effort to preserve, restore, and enhance the unique natural and human environment of the Lake Tahoe Region, while improving local communities and people’s interactions with our irreplaceable environment. For additional information, contact Jeff Cowen, Public Information Officer, at (775) 589-5278 or [email protected].