Babbitt visiting Tahoe; study warns of urban drainage

"We need to have a clear picture of the natural and human influences affecting Lake Tahoe to know how best to restore it," Babbitt said.

"This project is a classic case of sound science guiding environmental restoration," he said.

Babbitt on Wednesday plans to join researchers on the Inland Surveyor, the U.S. Geological Survey's boat that is exploring and mapping the deepest reaches of Lake Tahoe's floor.

Using acoustic sonar, scientists will develop high-resolution, three-dimensional digital data to create first-of-a-kind photographs of Tahoe's floor 1,600 feet below, Babbitt said.

The research will help reveal sediment patterns on the lake floor as well as a wide variety of sunken artifacts.

It's known there's a 169-foot mail and passenger steamer that was scuttled in about 400 feet of water half a century ago.

There are rumors of stage coaches that contain gold, locomotives and a B-52, all supposed to be on the bottom of the lake.

Visibility in the lake once reached down as far as 160 feet, the clearest waters in the world in the 1860s, Babbitt said.

"But that was before the Comstock Lode silver strike, clear-cutting of native trees and two-stroke engines," the secretary said in a statement this week.

"'Now, visibility in the lake is about 60 feet and falling," he said.

Historic logging and road building, lakeside construction, air pollution and increased traffic patters in the area all are blamed for the assault on Tahoe's clarity.

Preliminary results from a new study by scientists at the University of California-Davis suggest urban drainages may be playing a bigger role than suspected in accelerating algae growth that also harms clarity.

As much as 36 percent of the phosphorus deposited in the lake is coming from urban drainage and other areas where surface water does not drain into streams, said Alan Heyvaert, a leader of the study.

Such runoff apparently contributes more phosphorus than do the Tahoe Basin's 60-plus streams or what is deposited by shoreline erosion, by groundwater or from the air, he said.

"This, to us, is a surprising amount," Heyvaert told the Reno Gazette-Journal.

Phosphorous combines with nitrogen to nourish the algae. Urban runoff and fertilizer are full of phosphates, as is the sediment flowing into the lake from eroding areas.

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