Don’t eat the snow?

Tahoe-area scientists add chemicals to the clouds

It’s the time of year when skiers want feet upon feet of powdery snow. And so, if the conditions are right, scientists—sometimes on the ground, sometimes in an airplane—may be performing cloud seeding: a technical, scientific, winter-blizzard version of a rain dance.

Wintertime cloud seeding is a way to modify the weather by adding a seeding agent, silver iodide, to certain clouds to encourage snowfall. It’s a regular practice, but the idea of adding chemicals to the air still raises some eyebrows, especially considering that the Environmental Protection Agency regards silver iodide as a hazardous substance and toxic pollutant.

“[Sometimes] the natural precipitation process is somewhat inefficient,” explained cloud-seeding program director Arlen Huggins, of the Desert Research Institute. He said some clouds lack particles that help form ice, and that cloud seeding has been practiced in the United States for more than 50 years.

In October, the Desert Research Institute earned a $155,000 grant from the Truckee River Fund for cloud-seeding projects in the Tahoe area.

Cloud seeding is a process that starts by dissolving silver iodide in a solution of acetone and spraying that solution into a flame. This vaporizes the liquid, leaving behind a smoke plume of billions of silver-iodide particles. The wind carries these particles toward a targeted area and gives snowfall a boost.

Huggins says cloud seeding is only hazardous if the concentration is high enough, and that snow samples from seeding areas do not show higher levels of silver iodide.

“The bottom line is all the water samples, soil samples we take from our downwind area, we find concentrations that are more than 100 times less than what’s considered toxic to plant or animal life,” said Huggins.

Although scientists tend to agree that cloud seeding is effective, it’s not an answer to climate change and is but a small part of the solution when it comes to water-resource problems.

“Cloud seeding for snowfall is not something you do to get yourself out of a drought,” said Huggins. Instead, he said it’s something to do during normal storm years to facilitate water storage. “[When] it’s been dry for decades, there’s little you can do to try to change the supply side of that situation.”