Cloud seeding could bring more rain to South County

Santa Barbara County is planning cloud-seeding operations over the next five years that could increase rainfall over the southern portions of San Luis Obispo County.

The Santa Barbara County Water Agency will disperse silver iodide vapor into the atmosphere from airplanes and mountains during winter storms to promote the formation of raindrops, said Matt Naftaly, the water agency manager.

Under ideal circumstances, cloud seeding can increase rainfall by 20 percent, but normally increases are less than that, Naftaly said. The silver iodide particles work by providing a nucleus around which raindrops can form.

“Normally, dust would do this, but this simply increases the availability of seeds to increase the number of raindrops,” he said.

The goal is to increase rainfall in the watersheds behind Cachuma and Gibraltar reservoirs on the Santa Ynez River as well as behind Twitchell Reservoir on the Cuyama River. Portions of San Luis Obispo County could also be affected.

Cloud seeding is done during storms and is conducted between November and April. Aircraft or land-based units can be used to disperse the silver iodide into the air.

Airborne seeding is done over the land and Pacific Ocean. Ground-based seeding would be done from locations in the Santa Ynez and San Rafael mountain ranges and the Casmalia Hills.

The cloud seeding program costs about $300,000 a year and is paid for by the Santa Barbara County Water Agency and the various water districts that would benefit from it.

“The state Water Resources Control Board recognizes this as a safe method to increase water supplies,” Naftaly said.