State of the Lake
August 13, 2008
Smoke and ash from last summer’s Angora fire had a “small, though measurable” impact on Lake Tahoe’s clarity, according to a report released Tuesday by researchers.
Data detailing the fire’s effects is part of the second annual State of the Lake Report by scientists with the UC Davis Tahoe Environmental Research Center.
“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,” according to a statement from UC Davis.
The fire dropped about 11,000 to 18,500 pounds of nitrogen and between 850 and 1,750 pounds of phosphorus onto the lake, according to the report. These levels represent only 1 percent to 2 percent of the nitrogen and phosphorus that reach the lake each year.
Other avenues for pollutants from the fire to reach the lake ” such as urban runoff and soil disturbance ” make Angora’s total effect unknown as of yet.
“(The report) 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,” the statement indicates. “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.”
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Fine particles and nutrients ” both produced by wildfires ” reduce Lake Tahoe’s clarity. Nutrients do so by fueling algae growth in the lake.
The UC Davis report also indicates 2007 was the 14th-driest year on record, clarity improved over 2006, and the long-term warming trend first described by UC Davis last year continues.
“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,” according to the statement. “While lake temperature declined slightly in 2007, the long-term signs of global warming remain.”
Lake Tahoe also mixed all the way to the bottom in March 2007, the first time since 2001, according to the report. On average, the lake mixes throughout its entire depth every three years, according to the university. That’s about half the time it took for the most recent complete mixing.
Earlier this year, researchers from UC Davis warned that warming could decrease the regularity of deep-water mixing, potentially fueling algae blooms and making the bottom of the lake uninhabitable to many species.
The full 2008 state of the lake report is available online at http://terc.ucdavis.edu/stateofthelake/index.html.