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<br />Executin Summary <br /> <br />Recent drought conditions and the associated drop in Lake Powell storage has generated <br />renewed interest in means that might be used to better manage the water supplies for the seven <br />basin states that share water from the Colorado River system through the 1922 compact. Means <br />of augmenting the nows of the Colorado arc also being examined. One technique that has been <br />frequently mentioned is that of weather modification or "c]oud seeding" as it is more commonly <br />known. The Upper Colorado River Commission contracted for the preparation of this White <br />Paper. The goals of this paper were to consider the status of the weather modification field and <br />how cloud seeding could potentially be used to augment streamtlo\'.'s in the Colorado River <br />region. <br /> <br />The potential for use of cloud seeding to increase the amounts of naturally occurring <br />precipitation dates back to some early' discoveries and experiments. first conducted in the <br />laboratory and then in the atmosphere. in the late 1940's. Early enthusiasm lor such applications <br />led to the conduct of a number of research and operational programs during the 1950's. Some of <br />this early enthusiasm diminished due to difficulties in detecting the efTects of seeding on <br />precipitation. In a sense. the potential of cloud seeding was oversold during this period. <br />Additional research and operations were conducted with more realistic expectations beginning in <br />the 1960's and continuing to the present time. Some skepticism remains regarding the <br />cllcctivellcss of cloud seeding. although several professional societies nmv state that winter time <br />precipitation in mountainous areas can be increased on the order of 10%. Compelling evidence <br />exists for the positivc efTects of cloud seeding in augmenting watcr supplics in the west. although <br />proof in the strict scienlific sense is elusive. <br /> <br />Several operational winter cloud seeding programs have been conducted in the Sierra <br />Nevada tVlountains of Cali fomi a dating back to the early and mid-1950's in a couple of cases and <br />the early to mid 1960's in several other cases. Winter cloud seeding programs have also been <br />operated for a number of years in portions of Colorado. Utah. and Wyoming. For example. <br />programs in Utah date back to ] 974. Estimations of the effects on precipitation commonly <br />indicate seasonal increases of the order of 5% to 15%. <br /> <br />This paper identifies areas within the Colorado River Basin where a) new operational <br />"..inter c10lld seeding programs could be developed and b) existing programs enhanced through <br />additional funding to provide additional nmolT in the Colorado River system. These activities <br />would include new or expanded programs in the States of Arizona. Colorado. Utah and <br />Wyoming. Streamflow that contributes to Colorado River flows in these areas is primarily <br />gcnerated via melting snow from the higher elevation areas of these states. thus the <br />recommendation tor the focus on winter time programs. <br /> <br />A distinction is made between operational programs and research programs. Operational <br />programs arc conducted to achieve a specific objective or objectives: in this case. increases in <br />streamflow in [he Colorado River Basin. Cloud seeding research programs are conducted to <br />advance knowledge: perhaps to gain a better understanding of how cloud seeding works or to <br />