Wyoming to measure cloud seeding effectiveness

Published on Tuesday, January 31, 2006.
Last modified on 1/31/2006 at 11:25 am

"Everyone complains about the weather," Mark Twain famously noted, "but no one does anything about it."

But researchers in Wyoming are hoping to reduce complaints of lingering drought across the state by embarking on an ambitious five-year, $8.8 million pilot project aimed at increasing snowfall through cloud seeding.

Cloud seeding involves using planes and ground-based generators to spray plumes of silver iodide particles into clouds in an effort to increase precipitation.

Whether the practice is effective is still being debated.

"We received a lot of inquiries from conservation districts wanting the state to be pro-active in this area and look at the technology available," said Barry Lawrence of the Wyoming Water Development Commission.

Lawrence is managing Wyoming's cloud seeding project, which aims to study potential changes produced in winter precipitation over five years in the Wind River, Medicine Bow and Sierra Madre mountains.

"One water commissioner said to me, 'This is the first water project we're doing that addresses the source of supply,' " said Lawrence, "which is kind of a unique way of looking at it, but I guess he's right."

Key to Wyoming's program, and what differentiates it from similar efforts throughout the arid West, is that it runs over five years and aims to closely monitor results to gauge effectiveness.

Around $1.9 million of the project's budget will be used to measure results, Lawrence said.

"You won't have the operators who are doing the seeding coming up with estimates of their effectiveness," he said.

Weather Modification Inc., a company based in Fargo, N.D, will seed snow clouds over Wyoming, while another group from the National Center for Atmospheric Research in Boulder, Colo. will measure the results.

Running the project over five years is important, said Dan Breed, a researcher at the Boulder center who designed Wyoming's program.

He said it is only by studying results across several years that scientists can determine whether increased snowfall is resulting from seeding efforts, rather than natural variations in weather patterns.

Cloud seeding is tricky business, and achieving even 10 percent more winter precipitation would be a significant result, Breed said. By adding material to promising clouds, scientists hope to foster ice accumulation and snowfall.

"The essence of cloud seeding is adding particles which look a lot like ice," said Breed. "We add silver iodide to clouds to make more ice crystals.

"If you add more ice crystals to some clouds under some conditions, that can increase precipitation by making the cloud more efficient in transforming liquid water and water vapor (into snow), instead of it all just evaporating downwind."

In a process known to scientists since the 1940s, Breed said silver iodide particles, which mimic the structure of ice, help foster the aggregation of ice crystals, which then fall from the cloud as snow or other frozen precipitation.

Lawrence said successful cloud seeding might prove a cheap way for the state to add badly needed water to its reserves, particularly when compared with the cost of building pipelines, deep wells or reservoirs.

An increase of runoff from an additional 15 percent in snowpack in the program's target areas would produce extra water at a cost of about $8 per acre foot, Lawrence said.

That's a fraction of the more than $150 per acre foot that is the amortized cost of water stored in the state's new High Savery Dam, he said.

Much of the program's seeding will be done from ground-based generators located in national forests, and permits for those sites are still pending.

But crews already are taking baseline weather measurements around the state, said Bruce Boe, director of meteorology for Weather Modification Inc.

A specially equipped airplane based in Cheyenne has been gathering meteorological data throughout January, Boe said.

The flights aim to gather data and establish benchmarks on clouds and weather systems that are favorable for seeding.

Boe, whose company engages in cloud seeding operations around the world, said he is eager to see the results of Wyoming's pilot project.

"Those of us who've done it for so many years have seen so many cases that we're convinced it works," he said.

Contact Ruffin Prevost at rprevost@billingsgazette.com or (307) 527-7250.

Copyright © The Billings Gazette, a division of Lee Enterprises.


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