Cloud seeding suspended – we don’t need it
Mother Nature shouldn’t get all the credit for Lake Tahoe’s impressive snowpack.
Every winter – more during dry or normal winters than this one – Mother Nature gets some help from the Desert Research Institute.
For more than 30 years, DRI’s Cloud Seeding Program has increased the snowpack at Lake Tahoe and other areas of Nevada.
Not surprisingly, Tahoe’s cloud-seeding efforts were suspended Feb. 6. Tahoe’s snowpack is 162 percent.
“Typically, when the snowpack is above 150 percent this time of year, we don’t seed any more. It’s quite likely we won’t seed any more at Tahoe this year,” said Arlen Huggins, DRI associate research scientist. “In years like this that are really wet, people are always concerned we are adding to their grief. We do have suspension criteria. We don’t seed when the snowpack is at certain levels or if there’s any type of flood conditions, any type of natural weather phenomenon that’s creating its own havoc.”
Other areas of the state – such as the watersheds of the Walker and Carson rivers, the Ruby Mountains in the northeast part of Nevada and part of the Toiyabe range in central Nevada – have much less snow than Lake Tahoe. Cloud seeding continues there.
“The primary reason (for the cloud seeding) is to increase the snowpack and increase the snow runoff in the spring – and add to the water supply,” Huggins said.
The cloud seeding produces an estimated increase to the water supply each year of about 35,000 to 55,000 acre feet of water. One family uses about 1 acre foot of water each year – 330,000 gallons.
The program is funded by the state of Nevada. Operating cost is about $480,000 a year. A conservative estimate on the value of water produced by cloud seeding is more than $20 million.
Within the last 14 years, because of better technology, Huggins said, DRI has been able to increase the amount of equipment it uses and its efficiency, while not increasing costs.
How much difference does it make for the snowpack?
It depends on the weather.
“A year like this, percentage-wise, you’re going to add a very small percentage to the snowpack. Probably only a few percentage points,” Huggins said. “In a drier year, there might be a much higher percentage of the snowpack that came from cloud seeding. There could be as much as 10 percent in a dry or normal year. It really depends on how many storms you have and how often you can seed.”
There is “no magic involved” in cloud seeding, according to Arlen Huggins, Desert Research Institute associate research scientist.
“Cloud seeding is basically adding some type of material to allow ice to form in the cloud,” Huggins said.”Unless water droplets have something to form ice on, they remain water droplets and stay in clouds.”
Clouds need to have “nuclei” where ice can form.
It happens naturally, but DRI helps the process. Through machines placed on the tops of mountains or from DRI’s newly acquired airplane, silver iodide is released into the air. When it ends up in clouds, each particle acts as a nucleus for ice formation.
The process takes about 30 to 45 minutes, and the airplane or generators release the chemicals downwind from where DRI officials want the snow to fall.
Five of the mobile generators were placed west of Tahoe this year, and Huggins said as many as seven are used for the area during dry years. A generator consists of 6-foot high, 8-foot wide metal box containing computers solutions used to release the chemicals. On top of the boxes set 20-foot tall towers, which ensure the silver iodide is released above the snowpack.
Workers based in Stead, Nev., control the operations from computers there. Running the operation for Nevada takes four full-time employees and a few more wintertime workers.
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