The Santa Barbara County Water Agency (SBCWA) conducts a precipitation enhancement program, also known as "cloud seeding," to augment natural precipitation to increase surface water runoff in watersheds behind the major water reservoirs. These reservoirs include Cachuma Reservoir and Gibraltar Dam on the Santa Ynez River and Twitchell Reservoir on the Cuyama River near Santa Maria. The target areas of operation are located above the reservoirs and are illustrated on the map.
program has been in existence since 1981 and is based on research conducted
between 1957 and 1974 which showed that significant increases in rainfall could
be achieved by seeding convective bands during winter storm events. A summary
of the early research can be located here.
Most storms in Santa Barbara County are abundant in moisture but limited in condensation nuclei. Water droplets or ice particles form on microscopic condensation nuclei, which are 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 exists below the freezing point but does not freeze due to extremely low atmospheric pressure. Cloud seeding injects artificial hydroscopic material into the convective bands and cloud mass, providing a mechanism to move the moisture from the cloud mass to the surface of the earth where it is needed.
Seeding in Santa Barbara County is accomplished by using a combination of ground based sites and at times aircraft. There are currently seven land based sites being utilized. These sites are referred to as Automated High Output Ground Sites (AHOGS) and are illustrated in the map above. AHOGS located at Berros Peak (East Nipomo), Mount Lospe, Harris Grade, and Sudden Peak are used for the Twitchell Dam target area, while AHOGS located at Refugio Pass, West Camino Cielo and Gibraltar Road are used for the Santa Ynez target area. A video of an operational AHOGS and air seeding event can be viewed below by clicking on the photo.
SBCWA shares the cost of the operational program with local water purveyors throughout the County. The design of the program may change each year to reflect watershed and hydrologic conditions. Additionally, program modifications may be implemented based on storm severity, or the
program may be completely suspended as a result of fire and erosion potential.
The practice of precipitation enhancement in Santa Barbara County has proven to be a cost effective and positive addition to water resources management goals and objectives. An
historical target/control analysis was completed in 2015 which showed that the cloud seeding program plays a valuable role in increasing water supplies and protecting groundwater resources by increasing rainfall in seeded storms by approximately 20% in the Santa Ynez target area, and 9% in the
Twitchell Dam target area.
Cloud seeding programs are conducted throughout California and are common throughout the world. The SBCWA recognizes cloud seeding as a safe and cost effective means of enhancing water supplies. The California Department of Water Resources labels cloud seeding a "safe and effective means of augmenting local water supplies." The American Society of Civil Engineers (ASCE) recognizes cloud seeding and has produced an operations guidelines manual. The Weather Modification Association and the North American Weather Modification Council provide excellent information on international programs, studies, methodology, and seeding material. Santa Barbara's program is in compliance with the California Environmental Quality Act and conducted in accordance with all applicable laws and licensing.
Documents, Research, and Literature related to Santa Barbara weather enhancement:
Summary of Operations for Cloud Seeding Program for Santa Barbara County Water Year 2018-19 (Summary of the last operational precipitation enhancement season)
Santa Barbara County Cloud Seeding Program Mitigated Negative Declaration (This document summarizes the program and addresses significant environmental effects)
Cloud Seeding, The Environment & The Climate (This brochure created by the North American Weather Modification Council summarizes the basic science of cloud seeding)
Understanding Cold Season Cloud Seeding (This brochure created by the North American Weather Modification Council clearly summarizes concepts used in precipitation enhancement in coastal regions similar to Santa Barbara)
Material Safety Data Sheet for Silver Iodide (Silver Iodide is used as the artificial hydroscopic material for precipitation enhancement)