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<br /> <br />002342 <br /> <br />. <br /> <br />. <br /> <br />from members of the Weather Modification Association (commerical cloud <br />seeders), with specific identification of the source of these, and other <br />statements. <br /> <br />Orographic Precipitation <br />The greatest interest in weather modification in the Pacific Southwest <br />has been in enhancing orographic precipitation. Most of these efforts <br />have been to increase the snowpack, primarily in the Sierra Nevada <br />Mountains. Atmospheric scientists involved in weather modification, agree <br />almost unanimously that snowfall can be increased in mountainous regions <br />up to 300 square miles. Estimates vary from 5 to 30%, but 10% is about the <br />average prediction based on current technology. Scientists are divided <br />as to whether future techniques will improve appreciably on this 10%. <br />Uncertainties in this area of weather modification range from question <br />of conservation mass and energy and the complexities of natural precipita- <br />tion to social aspects. The concept of natural limits on increases is <br />extremely important in long range planning. <br />Two reiative1y large scale experiments to augment snowfall (the <br />Colorado River Basin Pilot Project and the Pyramid Lake Pilot Project), <br />have been carried out in recent years. Both have been completed and <br />the data are being analyzed. Final results from these 2 experiments <br />are not as yet available. Initial information indicates that <br />unexpected natural and manmade problems have Inade the analyses of <br />the projects more difficult than was expected. Currently, the <br />USBR is reanalyzing results from several relatively small scale <br />randomized experiments to augment snowfall which were carried out <br />independently at several state universities, in the West (Montana State, <br />Fresno State, New Mexico State, Colorado State, and Utah State). The <br /> <br />3 <br />