Cloud seeding considered to ease drought

by Mike Stark - Billings Gazette/Wyoming Bureau

As water-starved Wyoming enters another drought year, some are looking to wring more moisture from passing clouds.

Most everyone acknowledges that cloud seeding – where silver iodide is shot into clouds in the hopes of producing more precipitation – is a gamble. The question now is what risks the state is willing to take for benefits that may or may not materialize.

Ron Micheli, director of the Department of Agriculture and chair of the Governor’s Drought Management Task Force, said he’ll propose next month that the state not make a recommendation on cloud seeding, and leave the decision up to local conservation districts and county commissions.

"I can’t claim to be an expert, but my conclusion is there’s still a lot of work that needs to be done and a lot of unanswered questions," he said. "But I’m not saying there might not be benefits."

Wyoming could get an extra 10 to 20 percent of precipitation by seeding clouds, especially winter clouds over western mountain ranges, according to one of a handful of companies in the country that offers weather modification services.

"It’s not going to be a cure-all," said Don Griffith of North American Weather Consultants in Salt Lake City. But he said Wyoming could see success similar to a cloud-seeding program in Utah.

Cloud seeding, which can be done from the air or ground, allows silver iodide to be injected into certain kinds of clouds. The particles are supposed to turn frozen droplets of water into snowflakes that fall to the ground.

Although there are anecdotal reports that cloud seeding works, there isn’t enough scientific evidence to back up the claims, said Gabor Vali, a University of Wyoming professor and authority on cloud physics.

"What indications there are might be tantalizing, but it’s no more than that. There’s no solid evidence," he said. "Whoever claims to know is just putting on a show."

Montana looked at cloud seeding in the 1980s but state officials, amid concerns from North Dakota residents that their water might be stolen from the clouds, scrapped the idea.

Griffith said the "robbing Peter to pay Paul" argument doesn’t hold water.

"Ironically, research looking into that question indicates just the opposite," he said, adding that communities 50 to 100 miles downwind of seeding projects have seen more precipitation. Beyond that, the effects fizzle out, he said.

Still, Griffith admits that the research on cloud seeding doesn’t meet scientific criteria. But, he said, those who need water have been willing to accept the extra risks for the potential benefits.

Micheli said that’s what local groups in Wyoming will have to decide for themselves. He said he found it difficult to show with certainty whether cloud seeding works.

"I think it’s pretty hard to quantify," he said. "But obviously some people think it’s beneficial."

The Eden Valley Irrigation District has been using cloud seeding since the 1960s. A representative told the state drought committee that precipitation has increased by 11 percent, aiding agricultural producers.

Griffith, whose company could profit from programs in Wyoming, said that while most cloud-seeding programs are started during droughts, it’s best to run long-term programs. By providing consistently more moisture, water could be stored and used for dry years, he said.

"In my experience in the West, water supplies are typically short and usually over-appropriated," he said.

But Vali said the scientific community won’t be convinced until controlled experiments conducted over five or 10 years clearly prove the benefits of seeding.

"No state or local government or group has come forward to do that because it’s a huge commitment and a huge amount of money," he said.

And even though there’s evidence it might be working in Utah, Vali said, variations in weather systems could mean that Wyoming won’t get similar results.

"It’s a shot in the dark," he said. "They may get something, they may not."

(Reprinted with permission of the Billings Gazette in Billings, Mont.)