Cloud-seeding programs undertaken in Weber and Box Elder counties over the past two winters have significantly increased rainfall in both areas, a weather consultant says.
Weber County received 7 percent more rain than projected because of cloud seeding, and Box Elder logged 8 percent more, Don Griffith of North American Weather Consultants told the Utah Board of Water Resources on Friday.But because the two counties have only participated for two years, Griffith said, a better indication of the worth of cloud seeding is the 11 percent annual average rainfall increase in central and southern Utah.
The program has been under way in those sections of the state since 1974.
Griffith co-authored a paper on the Utah cloud seeding program that will be printed in an upcoming edition of the Journal of Weather Modification.
According to the article, the seeding program uses ground-based, manually operated silver iodide generators located in valley and foothill locations upwind of the higher elevation target areas.
Griffith said only once, in 1978, has cloud seeding produced less rainfall than projected.
State water planner Paul Gillette said he was happy to see one year down as it kept the data from "looking suspect."
Although cloud seeding is evidently working in Utah, Griffith said it's important to have reasonable expectations and to not anticipate normal conditions in abnormal years.
"If Utah is destined to receive 50 percent of normal precipitation, cloud seeding will probably only mean the state receives 55-60 percent of normal . . . but this additional moisture may prove to be quite valuable under sparse water conditions," he said.