Cloud Seeding

The Santa Barbara County Water Agency conducts a weather modification program better known as "cloudseeding" to augment rainfall and runoff in watersheds behind the major water reservoirs; Lake Cachuma and Gibraltar Dam on the Santa Ynez River and Twitchell Reservoir near Santa Maria. For the Twitchell Reservoir component of the program only the Huasna and Alamo watersheds are seeded, not the rain shadowed area of the Cuyama River drainage.

The operational program has been in existence since 1981 and follows research conducted between 1957 and 1974 that indicated significant increases in rainfall could be achieved by seeding convective bands embedded in winter storms that move through the area. Sponsors of the research programs included the National Science Foundation, Naval Weapons Center China Lake, U.S. Weather Bureau, U.S. Forest Service, State of California, University of California, Santa Barbara County and Ventura County. Research programs dating back to the 1950s were the result of pioneering work done in the field of weather modification in the late 1940s by Dr. Vincent Schaefer and Dr. Bernard Vonnegut.

The Water Agency shares the cost of the current operational program with local water purveyors where the Water Agency matches funds provided by local water purveyors on a year by year basis. The design of the program may change on a yearly basis to reflect watershed and hydrologic conditions. For example, if a wildfire affects a watershed, that watershed may not be seeded until it has recovered, as in the Zaca Fire and most recently the Whittier and Thomas Fires in the Santa Ynez watersheds. If reservoirs are filled the program may be curtailed and funds carried over to the next season. Not all storms are seeded – weak storms many times do not have the super-cooled water vapor content or proper wind field to promote significant results from seeding and very strong storms may not be seeded due to potential flooding in urban areas and perception of use of the program. No urban areas are targeted, just backcountry areas behind major reservoirs. View the cloudseeding target areas and ground sites from which cloudseeding operations are conducted.

Most storms that arrive in Santa Barbara County are abundant in moisture but limited in condensation nuclei. Water droplets or ice particles form on microscopic condensation nuclei, extremely small particles of dust or dirt in the atmosphere. Research has shown that many of these storms have embedded convective bands with super-cooled water vapor. Super-cooled water vapor is water vapor existing below the freezing point but does not freeze due to extremely low atmospheric pressure. By identifying these embedded convective bands and injecting artificial hydroscopic material into the cloud mass, cloudseeding provides a mechanism to move the moisture from the cloud mass to the surface of the earth where it is needed. Seeding is accomplished by both ground and aircraft. In some instances it is more cost effective to seed from the ground and in others with aircraft. Currently six land based sites are utilized, from north to south they are: Mt. Lospe, Harris Grade, Sudden Peak, Refugio Pass, West Camino Cielo and Gibraltar Road. View a short video clip of one of the ground sites in action.  

Cloudseeding programs are conducted throughout California and are common throughout the world. The SBCWA recognizes cloudseeding as a very safe and cost effective means of promoting adequate water supplies. The California Department of Water Resources labels cloudseeding a "safe and effective means of augmenting local water supplies." The American Society of Civil Engineers recognizes cloudseeding and has produced an operations guidelines manual. The Bureau of Reclamation has done several studies on effects and repeatedly found no negative impacts. The Weather Modification Association has a statement on silver toxicity which indicates no harmful effects. Santa Barbara"s program is in compliance with the California Environmental Quality Act and conducted in accordance with all applicable laws and licensing.

The cloudseeding program plays a valuable role in protecting groundwater resources by increasing rainfall in seeded storms by 18-22% (Solak, et al., 1996). Increased runoff captured by Gibraltar Dam and Lake Cachuma on the Santa Ynez River is used for a variety of purposes including municipal and industrial, direct irrigation of agriculture, recharge to the Santa Ynez River alluvial aquifer and Lompoc Groundwater basins and supplement of freshwater habitat. Increased runoff captured by Twitchell Reservoir is released slowly in the late spring and summer months in order to percolate into the heavily utilized Santa Maria Groundwater Basin.


Santa Barbara County Cloud Seeding Program Mitigated Negative Declaration

Summary of Operations for Cloud Seeding Program for Santa Barbara County Water Year 2018

Target Control Analysis

Santa Barbara County Cloudseeding Summary of Results

NAWC WM96-3 Potential Augmentation

Walker Basin Environmental Assessment

WMA AGI Toxicity 




Weather Modification Association  

North American Weather Modification Council

ASCE Policy Statement