Nevada Water Science Center

Lake Tahoe

Lake Tahoe, also known as the "Lake of the Sky", is an alpine lake that is world famous for its deep, clear water. Over the last half century, clarity in Lake Tahoe has declined by 30–40 feet or 1 foot per year. This decline in clarity has been attributed, in part, to nutrients and sediments delivered to the lake by its tributary streams and nutrients from groundwater inflow.

For decades, USGS has been involved with a wide range of scientific research and monitoring activities in the Lake Tahoe Basin. Water-related activities include stream quantity and quality, groundwater levels and quality, and lake levels and quality. Mapping activities include topographic, bathymetric, and geologic; land-cover and land-use change delineation; and socioeconomic modeling.

Map of the Lake Tahoe Basin

USGS Nevada Water Science Center currently has 14 streamflow gages on tributaries to Lake Tahoe.


Real-Time Streamflow :: Daily Values :: Peak-Flow :: Water Quality

Current Activities

Lake Tahoe Basin LiDAR

Lake Tahoe Organics

Lake Tahoe Tributary Monitoring


Lake Tahoe Bibliography: List of USGS Nevada WSC publications about Lake Tahoe, including cooperative State publications.


Lake of the Sky: USGS Tahoe Basin Science

How Do We Measure Lake Clarity?

In Lake Tahoe, the clarity of the water is usually measured using a device called a Secchi Disk. The Secchi disk can be a white or white and black, circular disk that is suspended on the end of a rope or cable. Scientists lower the disk from the side of a boat at different locations within the lake. The point at which the disk is no longer visible is known at the Secchi depth.


Reeling a Secchi Disk in to the boat


In 1968, the Secchi depth at Lake Tahoe was 102.4 feet. In 2010, the Secchi depth was 64.4 ft. A list of yearly Secchi depths are available from the U.C. Davis Tahoe Environmental Research Center.


Graph of the decline of water clarity at Lake Tahoe



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page Last Modified: May 1, 2012