Overview

The Weather Modification Program supports increased water supply in the Colorado River through funding of cloud seeding activities in Colorado, Utah and Wyoming by local funding agencies in the Lower Basin States. The program is coordinated by the North American Weather Modification Council (NAWMC). CRB staff represent the Six Agency Committee on the NAWMC, participating in regular NAWMC meetings and decision-making activities.

Background

Weather modification, commonly called cloud seeding, entails sending small particles into a cloud or fog to increase precipitation, and is practiced throughout the world due to its sound scientific basis, environmental safety, and strong regulatory controls. Cloud seeding can be used to increase water supply, reduce hail from thunderstorms, or reduce fog for increased visibility (e.g. at airports). The goal of cloud seeding for water supply is to modestly increase the overall amount of precipitation from a pre-existing, natural precipitation event.

Two cloud seeding modes are practiced: cold season and warm season, where the objectives are to increase snow and rain, respectively. In the Colorado River Basin, only cold season cloud seeding is practiced. The figure below shows cloud seeding areas in the Western United States involved with the NAWMC.

The North American Weather Modification Council (NAWMC)–of which California’s Six Agency Committee is a member–is a leading organization involved in coordinating cloud seeding activities in the United States and Canada, and provides many resources to learn more about the practice. The map below shows cloud seeding target areas for water supply in North America. The Weather Modification Association is an industry association focused on implementing cloud seeding activities; California is not involved with the WMA for activities in the Colorado River.

Weather modification in the Colorado River is jointly supported by three funding agencies in the Lower Basin: the Six Agency Committee (California), the Central Arizona Project (Arizona), and the Southern Nevada Water Authority (Nevada), with funding shared equally between each of these three agencies. This funding program supports cloud seeding activities for water supply enhancement in the Upper Basin states of Colorado, Utah and Wyoming, as follows:

• Colorado: San Juan mountain range
• Utah: Wasatch Plateau, High Uinta, Central, Southern and Book Cliffs
• Wyoming: Wind River and Sierra Madre mountain ranges