From Environment & Energy Daily (Annie Snider) via WyoFile:
As a painful reckoning sets in throughout the West, where the Colorado River Basin is in its 15th straight year of drought, desperate water managers are welcoming a new cloud-seeding study as rare good news.
The concept of cloud seeding — using aircraft or ground-based generators to inject microscopic particles of silver iodide into clouds around which ice crystals can form and fall as snow — dates back to the 1940s.
Today, ski resorts, water districts and farmers across the West swear by the practice to produce both snow and water, spending millions of dollars a year on machines and flights.
But proving that money is well-spent has been tricky. Because, while it might snow or rain after a cloud’s been seeded, it’s hard to know whether the seeding actually caused the precipitation…
Wyoming’s Legislature took the challenge and, buoyed by coffers filled from oil and gas severance taxes, poured $14 million into a major study over the past 10 years that employs the latest scientific techniques recommended by the NRC panel, as well as an independent evaluation team.
The topline findings, recently unveiled to the Legislature: Seeding the right storms the right way can produce 5 to 15 percent more precipitation. That could increase streamflows by as much as 3.7 percent, the researchers’ initial findings indicate.
The study also found seeding to have next to no downwind impact, suggesting seeding storms to get precipitation in one place is not decreasing precipitation elsewhere.
“We know that silver iodide produces ice crystals, so really it ends up being an engineering problem: Can the ice crystals get into the right cloud at the right place and can we do all this?” said Roy Rasmussen, a senior scientist with the National Center for Atmospheric Research who led the study’s outside evaluation team.
“That’s what the Wyoming program demonstrated: That, yes, they can do it,” he said. “With modern technologies — through satellite-controlled silver iodide generators, and with good forecasting, with good real-time modeling — we can figure out when the storms are right for seeding and apply the seeding, and there is a measurable effect.”
More cloud seeding coverage here.