Secretary of the Interior Bruce Babbitt will be in Tahoe City, Calif., Wednesday, Aug. 12, to join U.S. Geological Survey scientists in exploring and mapping the deepest reaches of the Lake Tahoe floor in search of explanations for the rapidly decreasing clarity in Tahoe's famously clear waters.

"In the late 1860s, when Mark Twain first came to Lake Tahoe, these were the clearest waters in the world, with water visibility of more than 160 feet. But that was before the Comstock Lode silver strike, clear-cutting of native trees, and two stroke engines," Babbitt said. "Now visibility in the Lake is about 60 feet and falling. We need to have a clear picture of the natural and human influences affecting Lake Tahoe to know how best to restore it. This project is a classic case of sound science guiding environmental restoration."

Babbitt will go aboard the USGS research vessel, the Inland Surveyor, to observe the use of acoustic sonar by U.S. Geologic Survey scientists. This technology will allow development of high-resolution, 3-dimensional digital data, providing researchers and the public first-of-their-kind photograph-like maps of the lake floor. The data will reveal lake floor sediment patterns, sunken artifacts, and establish a base map for future research by USGS and other scientific organizations. This information will be compared with maps made in the 1920s to study the changes in the lake in the past 70 years.

"This is a key road map for future research and restoration," Babbitt said. "We need a comprehensive understanding of all factors--particularly sedimentation patterns and rates and the exact contours and water volume
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Contact: Dale Cox
dacox@usgs.gov
(916) 997-4209
United States Geological Survey
4-Aug-1998