San Luis Obispo County considers cloud seeding

Mar 7, 2018

California officials are always on the lookout to enhance water sources. In San Luis Obispo County, rainfall has been about 21 to 30 percent of normal this season. For the first time, county officials are considering a cloud seeding program to increase the local water supply. 

The county needs more rain to fall on the area’s main municipal water sources - Lopez Lake and the Salinas Reservoir watershed - during what’s called "winter precipitation events." That’s a scientific way of saying: storms. How? One idea is cloud seeding; shooting particles of silver iodide, a chemical that mimics ice, into storm clouds from ground sites and from canisters mounted under airplane wings. The seeding takes place as a storm approaches, enabling raindrops and snowflakes to form more easily.

Ray Dienzo is with the county’s public works department.

"These particles go up into the clouds, form nuclei, and then the weight will act as rain," Dienzo said. "It will be precipitation, it mimics what nature already does, but in this case we kind of help it along to enhance it."

The county’s public works staff say the cloud seeding could potentially add anywhere from nine to 17 percent more rain to Central Coast reservoirs. But the county is sensitive to the question of environmental concerns, even though cloud seeding has been practiced in the Sierra Nevada since the early 1950s. Testing there by the Department of Water Resources has not found that silver iodide accumulates to toxic amounts in plants or animals.

San Luis Obispo County is taking public comment on an environmental document prepared about the proposal until March 20. The county board of supervisors are scheduled to consider the project in June.