CHEYENNE, Wyoming — State-funded research in Wyoming suggests that cloud seeding can increase mountain snowfall by up to 15 percent a year, has negligible environmental effects — and almost no impact on precipitation in surrounding areas.
In a nearly decade-long study, researchers found the increased snowpack produced more water in nearby rivers and streams that provide water for cities and farms. Conserving and increasing water supply is a top priority for many western U.S. states and other nations.
Governments around the world and some other U.S. states conduct cloud seeding to wring more rain and snow from the sky by injecting silver iodide into storm clouds. Its effectiveness is a matter of debate. Under the right conditions, silver iodide can help water droplets grow and fall to the ground. Critics say the technique is not proven and could pose a threat to the environment.
The Wyoming research, released Wednesday, goes a long way in advancing knowledge about enhancing snowfall from what are called orographic clouds that form over mountains, scientists said. Their findings will be presented to the American Meteorological Society annual meeting next month in Phoenix.
"I see this program as paving the way to a lot more detail science in orographic cloud seeding," said Roy M. Rasmussen, senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, who was involved in the Wyoming study.
Scientists did not study summer cloud seeding and rainfall. Research into rapidly-developing warm clouds is much more complicated, Rasmussen said.
Wyoming spent about $13 million for the research, which used ground-based seeding generators on the Wind River, Sierra Madre and Medicine Bow mountain ranges in the central and southern parts of the state. Working independently from the state and the cloud-seeding operator, NCAR scientists crunched and interpreted the data.
They found that snowpack was not affected outside the immediate cloud seeding areas.
A final research report on the Wyoming project will be submitted to scientific journals for review in coming months, according to Barry Lawrence, project manager with the Wyoming Water Development Office.
Rasmussen said the Wyoming study is unique in that it sought to quantify the effects of mountain cloud seeding.
"The work that we're doing is being followed by a lot of colleagues and operational cloud-seeding folks around the world," he said.
The Rocky Mountain snowpack is a key source of trillions of gallons of water for mountain and Great Plains states as well as drought-stricken California, Arizona, Nevada and Mexico.