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<br />Executive Summary <br /> <br />This paper provides a brief background of weather modification, information on existing <br />programs and current issues, and provides recommendations for the Colorado River <br />Basin States (Basin States) involvement or support of precipitation management through <br />weather modification efforts. <br /> <br />The purpose of winter cloud seeding to increase snowfall in mountainous areas is to <br />increase runoff for hydroelectricity and water supplies for downstream areas. Increases <br />in precipitation can improve soil moisture, stream flows, and reservoir levels. More <br />water storage in reservoirs can allow for increased power generation, irrigation, and <br />municipal and industrial use. Recreation, water quality, salinity reduction, fisheries, <br />forest health, sensitive species, ranching, and tourism can all benefit from additional <br />runoff. <br /> <br />Members of weather modification organizations, public agencies, and private sector <br />companies believe that cloud seeding has reached the point that a well managed program <br />including a proper design component can be implemented to produce cost-effective water <br />resources benefits. More research on the specific cause and effect relationship between <br />cloud seeding and additional water on the ground should be conducted as well. Any <br />proposed operational cloud seeding program should include a strong evaluation <br />component. <br /> <br />It is estimated that cloud seeding six major runoff-producing areas within the Colorado <br />River Basin could produce between 1.1 and 1.8 million acre-feet (mat) in the Upper <br />Basin (approximately 10% of the average annual stream flow) and an additional 830,000 <br />acre-feet in the Lower and adjacent basins. Of the total, it has been estimated that <br />approximately 1.7 maf would be available to reduce deficits and meet new demands. <br /> <br />Although there is wide discussion regarding the effectiveness of weather modification <br />since it began in the I940s, proponents of ongoing projects believe programs in Utah <br />have resulted in precipitation increases between 7 and 20%, at costs ofless that $20 per <br />acre-foot, which compares favorably with traditional water resources projects. The <br />programs currently in operation in Colorado and Utah demonstrate the success of weather <br />modification (WxMod) activities there. Ski areas, water authorities, and agricultural <br />users are the most common project sponsors. <br /> <br />There are several good reasons for the Basin States to continue its research on this topic. <br />One of the most important is the 2000-2004 Colorado River drought, which is a normal <br />part of the climate of the arid Western United States and Colorado River Basin. Others <br />are a general trend toward reduction in snowpack, increased water demands, as well as <br />the growing concern about reductions in precipitation due to inadvertent anthropogenic <br />modification to weather (air pollution). Factors to consider in deciding how to proceed <br />are that: new projects take 1-3 years to plan; planning is relatively inexpensive; there is a <br />real need for research and project funding; these projects are very cost-effective, and <br />there are existing programs with data that can be leveraged. <br /> <br />-i- <br />