by Margaret Moran
mmoran@sierrasun.com

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April 17, 2014
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Scientists seek runoff studies funding

In an ongoing effort to protect Lake Tahoe, scientists are developing an alternative way to trap stormwater runoff — although more funding is needed to complete the project.

Using lidar data, an aerial laser-scanning technique that is known for its accuracy, a research group has created land surface maps of locations around the basin that show paths water takes within urban areas surrounding the Lake.

The maps also identify small, natural depressions in the landscape that can trap runoff as an alternative to constructing stormwater treatment or detention basins.

“The traditional (methods) are very expensive,” said Geoffrey Schladow, director of the UC Davis Tahoe Environmental Research Center, who is involved in the project along with two colleagues at the University of Granada in Spain. “… We’re looking for smarter ways to do the job, and maybe even more effectively.”

By enlarging natural depressions in the topography and using excavated material to build a small retaining wall, runoff can be held back and allow it to infiltrate the ground rather than running directly into streams and Lake Tahoe.

To build such a detention basin, it would likely take days and cost approximately $20,000, making it less time-consuming and expensive to construct than traditional methods, Schladow said.

TERC is partnering with regional organizations such as the California Tahoe Conservancy to fund and build prototypes this summer and monitor their effectiveness moving forward.

Mapping of Incline Village, the South Shore and some West Shore locations have been completed with the project’s approximately $123,000 in Southern Nevada Public Land Management Act funding.

In order to complete mapping for all urbanized areas around the Lake in both states, $100,000 more is needed, Schladow said.

While other funding sources are being explored — and until money is secured — mapping has halted, he said.

Urban stormwater runoff is believed to be a major contributor to Lake clarity decline.

“I think dry conditions make people forget about stormwater,” Schladow said.

In March, it was announced that Lake clarity dropped five feet from 75.3 feet in 2012 to 70.1 feet in 2013. Despite that, clarity levels continued a decade-long trend of stabilization, according to the Tahoe Regional Planning Agency and University of California, Davis.

That clarity data was an average of 25 readings taken throughout the year. The last five readings, taken in November and December, showed clearer waters than measurements taken in 2012.

“Clarity in Lake Tahoe largely reflected what we saw in the weather in 2013,” Schladow said in a statement. “At the beginning of the year, clarity was lowered by large stream inflows. At the end of the year, the low inflows resulting from the drought conditions helped to improve clarity.”

Most runoff occurs during the winter and spring, when rain and snowmelt carry sediment from the land into the Lake.

“We recognize that more is needed to restore the lake to its historic clarity level, and science is showing that it can be done,” said Joanne Marchetta, executive director of the Tahoe Regional Planning Agency, in a statement. “Together, we can save one of the cleanest, purest lakes in the world.”


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The Record Courier Updated Apr 17, 2014 05:34PM Published Apr 17, 2014 09:22AM Copyright 2014 The Record Courier. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.