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<br />options for enhancing the West's water supply should be seriously examined, including weather <br />modification, commonly called cloud seeding. <br /> <br />1.2 Cloud Seeding as a Water Augmentation Option <br /> <br />Cloud seeding has been applied for diverse purposes, including rainfall and snowfall <br />augmentation and hail suppression. In this report, the meaning of the term "cloud seeding" is <br />limited to attempts to increase snowfall and runoff from mountain regions. <br /> <br />Cloud seeding cannot solve all the problems noted above. However, a well tested and validated <br />technology can offer an important, cost-effective tool for water resources management. A 10 pct <br />snowpack increase in unregulated mountain watersheds in the Upper Colorado River Basin is <br />estimated to increase April through July total runoff in most watersheds at least 10 pet. Runoff <br />increases up to 20 pct could be expected from some drainages, and less than 10 pet runoff <br />enhancement may result in watersheds with very permeable soils. Cloud seeding is one of few <br />nonstructural alternatives for increasing water supplies. Cloud seeding has the potential to not <br />only enhance water quantity and increase hydroelectric energy production, but also improve <br />water quality. For example, studies have shown that additional runoff from snowmelt in the <br />Colorado river can significantly reduce salinity. <br /> <br />Cloud seeding is an attractive approach to streamflow augmentation and water quality <br />improvement because it does not require major permanent construction or large fixed operation <br />and maintenance costs. A decision to employ cloud seeding can be made on a year-to-year basis <br />or even on a storm-to-storm basis within a season. More importantly, cloud seeding potentially <br />is one of the most cost-effective means for securing additional water in the Basin. Other options <br />are importation, desalination, evaporation' --- suppression, and vegetation management. <br />Importation and desalination have high construction costs. Current evaporation suppression <br />technology is not adequate for reservoirs on the Colorado River. Vegetation management <br />appears to be effective, for example, by cutting clearings within forest (Alexander et al., 1985) <br />and removing salt cedar and replacing it with native vegetation (Bureau of Reclamation, 1992). <br />However, opportunities for such manipulation may be limited. <br /> <br />Because the technology of cloud seeding has not been scientifically demonstrated as an effective <br />water management tool, many potential users are reluctant to apply it. Cloud seeding's <br />effectiveness in enhancing snowfall will continue to be questioned until adequate evidence is <br />obtained and published in refereed scientific literature where it can be given full scrutiny. After <br />the evidence withstands full examination, water users can be confident that cloud seeding is a <br />viable means of providing significant quantities of new water in a safe, cost-effective manner. <br />Thereafter, the technology likely will gain more widespread acceptance. <br /> <br />1.3 Program Purpose and Overview <br /> <br />The program proposed in this document is intended to provid~ convincing scientific evidence <br />that properly conducted seeding of winter orographic (mountain-induced) clouds can <br />significantly increase precipitation (snowfall) at two Upper Colorado River Basin (hereafter <br />Basin) locations. The magnitude of possible increases also will be documented. Once cloud <br />seeding is shown to have a firm scientific basis, potential users will be able to transfer the <br />technology to their specific area of interest. Some adaptation may be required for regions <br />outside the Basin if they have significantly different cloud and/or terrain characteristics. <br /> <br />2 <br /> <br />I <br />I <br />I <br />,t I <br />I <br />,I <br />'I <br />I <br />II <br />I <br />1 <br />I <br />J <br />, <br />I <br />I, <br />I <br />I <br />I <br />