Lake Tahoe Clarity Report Shows Highs and Lows of 2023
Annual report records trend of clearer winters, murkier summers
Lake Tahoe, Calif./Nev. – The clarity of Lake Tahoe’s famed blue waters in 2023 continued its years-long trend of improving during the winter and deteriorating during the summer. The annual clarity report, released today by the University of California, Davis – Tahoe Environmental Research Center, found that winter lake conditions were the clearest observed since 1983, with visibility of 91.8 feet under the surface, compared with 72.2 feet in 2022.
Summer months tell a different story, marking the fifth murkiest on record with an average of 53.5 feet, compared with 68.9 feet in 2022. Overall, the annual average for lake clarity dropped to 68.2 feet from its 2022 value of 71.9 feet.
“It’s important to understand the short-term changes but even more important to be thinking about how this lies in the context of the longer-term trends,” said Alexander Forrest, interim director of the UC Davis Tahoe Environmental Research Center.
Research buoy from Tahoe Environmental Research Center in May 2023. Credit: Brandon Berry, UC Davis
Search for clarity
UC Davis has been measuring clarity and other health indicators at Lake Tahoe since 1968. Clarity is measured as the depth to which a 10-inch white disk, called a Secchi disk, remains visible when lowered into the water. Lake Tahoe’s clarity is just one measure of the health of the watershed, but measurements of clarity loss in the 1950s and 1960s by the UC Davis Tahoe Environmental Research Center became central to efforts to protect the watershed from pollution and unplanned development.
UC Davis works with the Tahoe Science Advisory Council and partners across the Tahoe Basin to help inform policymakers and the community on strategies to protect the lake and stabilize the decline in clarity that occurred following the mid-20th century development boom.
In 1969, the states of Nevada and California created the Tahoe Regional Planning Agency (TRPA) to lead the collaborative effort to protect and restore Lake Tahoe, to set environmental standards, and to better manage growth and development in the region.
“Thanks to the bi-state partnership, Lake Tahoe is one of the most protected watersheds in the nation,” TRPA Executive Director Julie Regan said. “The science community has played a pivotal role in the drive toward environmental restoration, and we’re proud of the progress we’ve collectively made on Lake Tahoe’s clarity over the decades. What happens on the land here affects the lake, and we continue to look to science to inform and prioritize Tahoe’s restoration projects.”
Under the Lake Tahoe Environmental Improvement Program, or EIP, the states of California and Nevada along with more than 80 public and private organizations are actively working to restore lake clarity to its historic 97.4 feet. EIP partners have implemented hundreds of projects to restore the filtering function of wetlands and treat stormwater runoff.
Plankton, plastic, and particles
The clarity report attributes 2023’s clearer winter months (December 2022 through March 2023) to deep mixing events that brought clear water to the surface from the bottom of Lake Tahoe. After the clear winter months, the report highlighted the role of runoff and plankton in the observed low summer clarity values.
Read more at UC Davis Tahoe Environmental Research Center.
Media Resources
· Alexander Forrest, UC Davis Tahoe Environmental Research Center, alforrest@ucdavis.edu
· Jeff Cowen, Tahoe Regional Planning Agency, 775-589-5278, jcowen@trpa.gov
· Andy Fell, UC Davis News and Media Relations, 530-304-8888, ahfell@ucdavis.edu