How much environmental damage? Experts say Angora fire will hurt lake clarity; extent of impact remains to be seen
June 26, 2007
As the Angora fire’s sooty ashes drop into Lake Tahoe’s crystal waters, the expectations for lake clarity are falling as well.
“We can expect this to have a negative impact on the clarity of the lake, the extent of which depends on a number of factors,” said Charles Goldman, director of the UC Davis Tahoe Environmental Research Group.
Scientists are sure the fire’s devastation will cause environmental damage to the lake and the Lake Tahoe Basin: The only question is how much damage?
“There will be a clear short-term impact and perhaps a long-term impact, but we don’t know the extent of that yet,” said John Reuter of TERC.
The immediate effects of the fire stem from the ash, soot and other pollutants falling into the lake. Because it comes from vegetation, the ash is full of nitrogen and phosphorus that stimulate algae just like fertilizer. The ash will send algae into a growth spurt in just 24 hours, Reuter said. UC Davis researchers will be monitoring the algae growth, but they expect to see it peak in the next one to two weeks before dropping off.
“There is going to be a very significant impact to water clarity and algael growth on the South Shore,” he said.
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The additional nitrogen and phosphorus from the ash will also stay in the lake, recycling through its depths for five to 20 years, spurring algae growth for years to come. Additionally, any dust, debris or particles from the fire impact clarity.
“Fire sediments settle so slowly they will impact transparency for a longer period of time,” Goldman said.
Ash falling from the sky is not the scientists’ biggest worry, however. It is the potential runoff into Lake Tahoe from the steep, burned slopes of the fire.
“The area burned is 5 percent to 10 percent of the watershed of the Upper Truckee River,” Reuter said.
If Angora Creek is filled with sediment from fall and spring rains, that will drain into the Upper Truckee River which is Lake Tahoe’s largest tributary. The environmental damage from the runoff depends on the type of precipitation (rain is more harmful than snow), the nature of the soil, the steepness of the slope and how much mitigation is accomplished before the wet season, Goldman said.
“We don’t know how many years it will take for that watershed to stablize,” Goldman said.
U.S. Forest Service fuels officer Dave Marlow said the Burned Area Emergency Recovery (BAER) team is already in place to assess a plan for emergency watershed restoration treatments. However, it takes years to heal a forest, he cautioned, just as it takes decades to grow a tree. Impacts on wildlife are yet to be assessed by the BAER team, but Tahoe Regional Planning Agency spokesman Jeff Cowen said there are little hopes for the two goshawk nests and the spotted owl nest in the burn area.
Cowen said the TRPA had invested $7 million worth of Environmental Improvement Program projects in the area, one of which was a stream and fisheries restoration of Angora Creek.
For TRPA Executive Director John Singlaub, the mental picture keeps coming back to him of the charcoal he saw washed up on shore at Edgewood Beach.
“This is really bad news,” Singlaub said.