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<br />flowing over mountains offers the best prospects for increasing precipitation in an <br />economically-viable manner." Among their recommendations: <br /> <br />. Operational cloud-seeding projects should be strengthened by allowing an <br />independent evaluation of the results of seeding. This should include <br />measurements of physical response variables and a randomized statistical <br />component; <br /> <br />. It is essential that basic measurements to support and evaluate the seeding <br />material and seeding hypothesis proposed for any weather modification <br />experiments be conducted before and during the project, and; <br /> <br />. Weather modification programmes are encouraged to utilize new observational <br />tools and numerical modeling capabilities in the design, guidance and evaluations <br />of field projects. <br /> <br />II. CURRENT ISSUES <br /> <br />Purpose and Need <br />Many believe that WxMod technology has developed into an effective and economic tool <br />for increasing water yields. Cloud seeding is most effective under normal or near-normal <br />weather conditions; but the benefits during dry years cannot be ignored. The technology <br />is best used as a long-term water management tool rather than an activity to be <br />undertaken during drought. During droughts there are few clouds suitable for seeding, <br />and during wet winters there is enough precipitation so seeding operations would not be <br />necessary. Drought is a normal part ofthe climate in the arid Western U.S. and Colorado <br />Basin, and research using tree ring data has shown that far more severe and lengthy <br />droughts have occurred than the one of the last six years (U.S. Geological Survey <br />(USGS),2004). In the last century (1925-2000), there have been widespread declines in <br />mountain snowpack of western North America, particularly since midcentury (Mote et <br />aI., 2005) The authors of this investigation point to several climate studies suggesting <br />that this trend will continue and even accelerate. Perhaps the foremost concern is that, <br />even outside of drought periods, the consumptive use of water in the West continues to <br />grow rapidly, largely to explosive urban growth. This situation has already caused major <br />water conflicts and is expected to worsen in the coming years unless significant action is <br />taken (DOl, 2003). While snowpack is declining, demand for water is increasing. <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 /> <br />-10- <br />