UC: Lake Tahoe 2007 Was Warm and Dry, with More Clarity

University of California, Davis's annual Lake Tahoe health report finds that the long-term warming trend first described last year continues, that 2007 was the 14th driest year on record, and that clarity improved over 2006.

Issued on Aug. 12, the "Tahoe: State of the Lake Report 2008" says that the impact of smoke and ash from last summer's Angora Fire on the lake's clarity was small, though measurable. However, it cautions that it is too early to say what the impact from pollutants carried to the lake by streams and urban runoff in the burn area will be. A consortium of researchers is monitoring the long-term effects of the fire, which burned 3,100 acres at Lake Tahoe; the report says the fire's impact will not be known for several years.

The annual review is intended to give the public a better understanding of the changes occurring in the Tahoe Basin on a year-to-year basis and to place current conditions within a historical perspective.

Last year's inaugural State of the Lake Report bore the disturbing news that the climate in the Lake Tahoe Basin is warming up -- nights and lake waters are warmer, cold days are fewer, and less precipitation falls as snow. While lake temperature declined slightly in 2007, the long-term signs of global warming remain.

In this year's report, researchers had better news about trends in lake clarity. Using the most recent Secchi depth data and applying a sophisticated statistical approach, they found that the historical rate of decline in clarity apparently slowed between 2001 and 2007. Researchers caution that this finding is tentative and future measurements could reverse the improved trend.

The report is free at http://terc.ucdavis.edu.

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