Science fiction hits the ground in Tahoe
January 30, 2007
Who needs weather gods when scientists abound?
With the driest winter in 17 years and no storms on the horizon, a weather-inducing technique may be what is needed to save the Sierra snowpack this season.
The Desert Research Institute’s cloud seeding program has been conducted in Tahoe since the 1960s. Ground-based generators are used to burn a solution of silver iodide, sodium iodide and salt in acetone to create more snowfall from winter storms.
The mountaintop generators, or a plane, shoot the particles of silver iodide into clouds to help form the ice crystals. It can take anywhere from 30 minutes to an hour for the ice crystals to turn into snow, said Arlen Huggins, who runs the snow seeding program in Nevada and Tahoe and works as an associate research scientist with the Desert Research Institute.
“If the seeding generator is near the cloud base, it is almost instantaneous to create ice crystals,” Huggins said. “It doesn’t matter if it is falling in the east side of the lake or west of the lake, as long as it is getting in the Basin.”
Five generators are situated around the Tahoe area. Kingvale, Bunker Hill, Ward Peak, Barker Pass and an area along Highway 50 outside of Desolation Wilderness all house the equipment. Cloud seeding adds an average of 60,000 acre-feet of water to Nevada and Tahoe each year, Huggins said.
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Researchers have seeded clouds five times in Tahoe since Nov. 11. The last seeding occurred on Jan. 4. Huggins said it takes very specific weather conditions for the practice to work.
The temperature has to be at least 24 degrees at mountain top level, clouds must be present in the area, a southwesterly to northwesterly wind must be blowing and sufficient liquid water must be carried in the clouds, Huggins said.
He said the institute uses satellite images from the National Weather Service and other instrumentation to determine if conditions are optimal to begin the weather modification.
The Institute added two generators to Tahoe this year because of dry conditions. Tahoe is at 43 percent the normal snow pack, and Truckee is at 48 percent, according to the Natural Resources Conservation Service.
Jim Wallman, a meteorologist with the National Weather Service in Reno, said the snowpack from the Truckee Basin to Walker River Basin in Nevada is 35 to 40 percent below average.
No storms are forecasted, Wallman said. But researchers will be cloud seeding as often as possible this winter to squeeze as much moisture as possible from the dry winter.
The last time Tahoe had a winter this dry was in 1990 to 1991, he said.
“We’ve had other dry years, but nothing this dry,” Wallman said.