Nevada Focus: Mappers get to the bottom of Tahoe

Since it went on-line Jan. 16, Lake Tahoe's "virtual library" had about 3,000 visits in its first seven months on the Internet. But after the bathymetry of Lake Tahoe was put on the web site in mid-August, the number of visits has risen to 12,000.

"I watch the hits and it's really climbed dramatically. The bathymetry has really attracted a lot of attention," says Alexander Evans, the site's webmaster and a scientist with the U.S. Geological Survey's National Mapping Division in Menlo Park.

Between Aug. 6 and Aug. 13, the USGS' coastal and marine geology group mapped the floor of Lake Tahoe using acoustic sonar aboard the research vessel Inland Surveyor.

The mapping revealed lake floor sediment patterns, sunken artifacts and photograph-like maps of the bottom of Lake Tahoe.

"This is a key road map for future research and restoration," Interior Secretary Bruce Babbitt said in an online press release. "We need a comprehensive understanding of all factors - particularly sedimentation patterns and rates and the exact contours and water volume - so that we can accurately predict what work will be most effective in restoring clarity to the lake."

High resolution, three-dimensional digital photographs are included on the Lake Tahoe Data Clearinghouse site, showing the lake's depths in multi-colors and pulling out different views of Lake Tahoe from under the water.

The Lake Tahoe Data Clearinghouse provides data from the USGS and has links to other Tahoe-related agencies such as the U.S. Forest Service, the National Resource Conservation Service, the Tahoe Regional Planning Agency and the U.S. Environmental Protection Agency, among others.

It was started following the Presidential Forum in July 1997.

Many Tahoe agencies use Geographical Information Systems software to create maps and data banks for their use. The Lake Tahoe Data Clearinghouse is trying to post that information on the web site or link it to other web sites so it can be used by all basin agencies, scientists and interested people.

An example might be a map by the U.S. Forest Service of the basin's timber management which the TRPA could use instead of creating its own map or by overlaying new information on it such as stream zones. As the webmaster, Evans tries to keep up on what different agencies are doing and help them put their work on-line.

"It's trying to bridge a little bit for these different agencies. People weren't talking about what they had. Now they do not have to re-create something that has already been done," Evans said.

The coordination helps the agencies save time which results in a savings for taxpayers, he added.

Evans says his favorite part of the web site is the e-mail he receives from people using it.

"It's fun to see a regular taxpayer using this stuff," Evans says, noting that one man from Idaho used the web site to download digital files on elevation and topographical maps and then create a hiking map.

He has received e-mail from scuba divers who agree that Lake Tahoe's clarity has declined over the years, as well as a note from a 36-year resident who agreed with the push to improve Tahoe's clarity.

"They come from all over the world," he said, citing Internet visits from Canada, Chile, Australia, Germany and Japan.

The Lake Tahoe Data Clearinghouse is an easy-to-follow site which provides questions and help about downloading files, as well as information on various Tahoe agencies, the Presidential Forum and its status report on "deliverables" that the forum has or will produce.

There are aerial photos of Lake Tahoe, watershed maps, TRPA plan area statement maps, land capability maps, topographical maps, water data, scientific reports on various Tahoe subjects and even the day-to-day log of the Inland Surveyor while it mapped the bottom of Lake Tahoe.

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The web site is located at http://blt.wr.usgs.gov/

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