Impact of the Angora fire on water clarity
August 16, 2007
Researchers are anticipating that the run-off from the next year’s
snowmelt following the recent Angora fire will affect Tahoe’s clarity. “Angora had short term immediate impact,” said John Reuter from UC Davis Tahoe Research Center “but data is still being analyzed,” he said. It is already known that during those two weeks normal levels were exceeded by more than three times. But the real danger is yet to come.
Pollutants threatening Tahoe
One of the biggest ecological problems of the Tahoe basin has been the water clarity. For the past 40 years the lake has been losing about a foot of transparency per year, and is now down to approximately 67 feet. In the first few days of the fire, air pollution increased about 4-5 times on average, and 130 times at south shore. Ashes, soot, and waste from the burnt forest were found floating in the water, and nitrogen and phosphorus from vegetation were also seeping into the lake. The most exact information about the Angora’s effect on water clarity won’t be known until early 2008, according to Reuter. The most perilous consequence of the fire, however, is the run-off after a heavy rain, or the winter snowpack starts to melt. This will hurt the lake the most. Because the waste comes mainly from an urbanized area, the frun-off won’t be organic only.
“Run-offs that will come into the lake with rainfalls will hit the erosion and there will be less infiltration,” said Reuter.
Since the Angora creek drains into the upper Truckee River, changes in the river’s water quality are also expected.
It will probably take many years before the watershed will stabilize. The process of pollution will be hard to stop, because the water of Lake Tahoe is constantly mixing. The real damage will be known when the final research is published.
Depth measurements techniques About every 12 days scientists measure the optical clarity of the water. They use a Secchi disk, an instrument similar to a dinner plate, that when lowered into the water helps determine clearness of the lake. Main contributors to the decline of clarity are pollutants falling into the lake from the air, run-offs and algae. Brant Allen, a researcher for UC Davis, said the quality is dropping “because of material that falls into the lake from the sky and washes into the lake from the shore, such as auto exhaust, fireplace smoke, road dust, urban runoff and soil particles.”
In addition, some of the destructive material becomes a fertilizer for the algae.
Related posts: [ Tahoe Summit: 10 years later ] [ Are slash mats worth the cost? ] [ Delicia Spees talks about the Angora fire ] [ Angora homeowners going green ] [ Light bulb moment: Turn it off ]
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