Hoping to wring water from the skies, a parched Los Angeles County plans to launch an $800,000 cloud-seeding project in the San Gabriel Mountains that officials believe will boost rainfall and raise the levels of local reservoirs.
The project, which will rely on injecting clouds with silver iodide particles, has won county supervisors' backing and is slated to begin this winter.
"We're basically coaxing Mother Nature to give us 15% more rain than there would be otherwise," said county civil engineer William Saunders. He said the county did seeding for several decades, beginning in the 1950s.
This time, officials decided to resume the program after a seven-year lapse caused by concerns over mudslides in some mountain areas ravaged by brush fires.
With California gripped by dry weather and Gov. Arnold Schwarzenegger declaring a statewide drought, cloud-seeding is attracting both fresh attention and skeptics.
Critics throughout the West have long dismissed seeding as a dubious technological rain dance. They worry it can trigger landslides, such as the deadly one in the San Gabriel foothills 30 years ago.
Some water experts, including Peter Gleick at the nonprofit Pacific Institute, a nonpartisan think tank in Oakland, believe public funds would be better spent promoting proven water-conservation measures, such as low-flow toilets.
"It's a bit of a sign of desperation," Gleick said. "They've been doing cloud seeding for decades, but we've never clearly been able to show if it's what we've done or what nature has provided."
That's because researchers who try to prove seeding's efficacy face unique roadblocks. Rain forms in nature, not in a laboratory, and scientists can't very well seed one cloud and leave another one unseeded as a "control cloud."
Also, cloud behavior varies widely.
"To have them be in the right place at the right time, that's where it gets really complicated," said scientist Daniel W. Breed, who studies cloud physics and precipitation at the National Center for Atmospheric Research, a federally funded center in Boulder, Colo.
When county public works officials estimate that seeding will increase rain 15%, for instance, they're depending on a 36-year-old county analysis that compares rainfall from a decade of seeding with rainfall during the previous 20 years.
The National Academy of Sciences released a report in 2003 calling cloud seeding unproven and urged more thorough study.
