U.S. Water News Online
RENO, Nev. — Scientists say Mother Nature helped limit environmental damage to Lake Tahoe after last year's Angora fire that burned 3,100 acres and destroyed 254 homes.
While experts worried that excessive runoff would deposit large quantities of sediment into the lake, the area was spared heavy downpours last summer, and this spring was cool, allowing the snow to melt gradually.
Monitoring continues to determine whether any pollutants are migrating off the Angora fire area and into streams and rivers flowing toward Lake Tahoe.
"We've been very fortunate," said Nancy Alvarez, a hydrologist with the U.S. Geological Survey. "The weather was really good to us this year."
The USGS, Desert Research Institute and University of California, Davis are monitoring the waters of Angora Creek and the Upper Truckee River, Tahoe's largest tributary, for pollutants originating from within the fire area.
Sparked by an illegal campfire on June 24, 2007, the Angora fire exploded out of the Angora Creek drainage outside South Lake Tahoe.
Land managers and scientists were concerned that ash, sediment and algae nutrients could enter Angora Creek, flow into the Upper Truckee River and ultimately reach Lake Tahoe. The result could be an algae bloom and other degradation to the landmark lake.
"The danger was there, and it was significant," said Alan Heyvaert, an assistant research professor at the institute. "There was a lot of concern."
The first 12 months after the fire posed the most immediate hazard. Experts said a number of lucky breaks occurred.
For one, there were no major thunderstorms or heavy rainfall over the burn area.
During the winter, there were no big rain-on-snow events which could have caused heavy runoff and erosion.
And this spring came was relatively cool, allowing snow to melt gradually and runoff to come at a measured pace.
"It was a fairly cool spring, so you didn't get that big flushing out," said John Reuter, associate director of the Lake Tahoe Center for Environmental Science at UC Davis.
With a fast snowmelt, Angora Creek could have topped its banks and picked up pollutants, "but that just didn't happen," Reuter said.
The area has had a year for vegetation to begin to take hold, and that will help reduce danger of fire-area runoff from polluting Lake Tahoe, Reuter said.
"The impact is always going to be the greatest the year after the fire," Reuter said. "Having that extra year has reduced the risk somewhat. It's still there, but it's not as severe."