Lake Tahoe Clarity

Lake Tahoe's clarity is measured in open waters using a Secchi disk - a circular, white disk resembling a dinner plate - that is lowered slowly in the water. The depth at which the disk is no longer visible is recorded as the Secchi depth. The clearer the water is, the deeper the Secchi disk can be seen. Standardized methods for measuring Secchi depth at Lake Tahoe have been applied since the late 1960s. The University of California Davis' Tahoe Environmental Research Center (UCD TERC) performs 25-35 measurements throughout the year and reports the annual average Secchi depth in the annual State of the Lake Report.

Average Annual Lake Clarity Update - May 19, 2017


Data released today by the University of California, Davis Tahoe Environmental Research Center (TERC) and the Tahoe Regional Planning Agency reported Tahoe's 2016 average annual clarity level at 69.2 feet. This 3.9 foot decrease from the previous year is still more than 5 feet greater than the lowest recorded average of 64.1 feet in 1997.


Clarity levels increased in winter and decreased in summer. Winter clarity (December 2015 through March 2016) increased by 11.7 feet and  the 83.3 feet average was the highest, or clearest, recorded since 2012.


However, the summer declines were so large, they outweighed the improving winter clarity. For a second consecutive year, TERC researchers attributed the disappointing summer values to the continuing effects of climate change.   


Despite 2016’s summer decline, the data record indicates the long-term trend of clarity decline ended about 15 years ago. Since then, clarity has hovered around a value of 71 feet, but with sizable inter-annual and seasonal variability.


Click here to access the full UCD TERC press release.


Learn More



For more information on the Annual State of the Lake Report visit UC Davis Tahoe Environmental Research Center Website





Learn more about water quality in the Lake Tahoe Basin and other environmental indicators on the Lake Tahoe Info Website.