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<br />Summar)' <br /> <br />The results cited from both research and operational programs conducted in the <br />Intermountain West suggest a reasonable expectation of 5-15% increases in winter precipitation <br />from properly designed and conducted winter programs. This range of increases is consistent <br />with those included in ....'eather modification policy statements of the American :vleteorological <br />Society. the Weather Modification Association and the World f\'leteorological Organization. <br /> <br />8.0 Typical Benefit/Cost Ratios <br /> <br />In the design of new \....inter cloud seeding programs. the estimated value of the additional <br />water expected via implementation of the sceding program is frcquently compared to the <br />estimated costs of conducting the program. This information. frequently expressed as a ratio of <br />benefits/costs, can be used to assess whether the program appears to be feasible in an economic <br />framework. Other assessmenls may be neccssary to determinc if a proposed project appears <br />feasiblc scientifically. Benefit/cost ratios greater than 1.0 are obviously dcsired. An update to a <br />publication of the American Society of Civil Engineers (ASCI~. 1995) to be publishcd carly in <br />2006 recommends a ratio of approximately 5/1 to consider a program feasible. Some opcrational <br />programs are currently being conductcd \vith somewhat lower ratios (e,g.. for example <br />approximately 3/1) which is a decision that certainly can be madc by sponsors of programs. <br />These criteria are directed at operational programs. Research programs are more expensive to <br />conduct and typically do not undergo such an economic justification. <br /> <br />Some cstimatcs of bene till cost ratios of winter opcrational (or primarily operational) <br />programs have been cited in the literature. Henderson (2003) examined six long.tenn programs <br />being conducted in California. Hc cstimated benctillcost ratios. primarily drivcn by the value of <br />additional hydroelectric energy due to enhanced streamllows. range from 13/1 to 61/1 for <br />increases of 2-9% in additional runoff. These would bc primary benefits. As is oftcn the case in <br />thesc typcs of asscssments. there w'ill also be secondary benefits. For example. since the <br />generation of hydroelectric energy is non-consumptive. the additional streamflow could also be <br />subsequently used for irrigatcd agriculture or culinary \\'ater purposes. The estimated avcrage <br />cost of producing a 6% incrcase in strcamllow was $3.27 per acre foot for these six programs. <br /> <br />An analysis of benefilleost ratios on a four season program conducted on the uppcr noise <br />Rivcr drainage ofwcst celltralldaho yielded an estimatcd bcnefit/cost ratio of9.7/1. associatcd <br />with an cstimated average increasc of 12% in sno\v \\'ah:r content (GriOith and Solak. 2002). <br />Again. this was strictly based upon enhanced hydroelectric generation: the value of the additional <br />water for downstrcam uses was not included in the calculation. The estimaled average cost of <br />producing the additional strcamflow was $0.44 per acre foot for the four seasons. <br /> <br />A feasibility/design study was perfonned by Weather Modilication. Inc. (WMI) of Fargo. <br />North Dakota for the Wyoming Water Devclopment Commission (WMl. 2005). This study <br />included cstimatcs of thc amount and value of water that might be produced from a winter cloud <br />seeding program in the Wind River. Medicine now and Sierra Madre Ranges of Wyoming. The <br />calculation of the amount ofwatcr was driven by an assumed 10% incrcase in precipitation and <br />resultant 8% incrcasc in runoff. A range of estimated benelitlcost ratios of 2.4/1 to 4.7/1 were thc <br />