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1 <br />1 <br />A <br />11 <br />G <br />1. INTRODUCTION <br />1.1. General Discussion <br />This document presents a proposed plan for the conduct of an operational cloud seeding project aimed at <br />increasing winter precipitation (snowfall) in the high elevation headwaters area of the North Platte River <br />Basin (hereafter Headwaters Region). The scientific basis lies largely in the increase in information on <br />the treatment of winter orographic (mountain barrier induced) clouds in the western United States in the <br />past 20 years. Studies were sponsored /conducted by the United States Bureau of Reclamation <br />(Reclamation), National Oceanic and Atmospheric Administration (NOAA), National Center for <br />Atmospheric Research (NCAR), Colorado State University, Desert Research Institute of the University of <br />Nevada at Reno, University of Wyoming and others. Cloud studies and seeding projects of particular <br />interest here were conducted at the Headwaters Region, the Grand Mesa of west - central Colorado, the <br />Wasatch Mountains of Utah, the Sierras of California, the Bridger Range of Montana, and the Colorado <br />central mountains (projects are described and discussed in appendix A, sections 7 and 8). These studies <br />conducted many seeding trials to determine cloud responses to treatment. The projects also studied <br />natural cloud processes. The diversity of study areas and weather conditions provided data for analysis <br />covering a broad spectrum of conditions, thus broadening the knowledge base and understanding of cloud <br />precipitation processes and treatment possibilities. Results from these recent projects provide the <br />scientific basis and methodology for the proposed cloud seeding program presented here. <br />There is support for cloud seeding from professional organizations. The current policy statement of the <br />American Meteorological Society (AMS) on the status of precipitation increase from supercooled <br />orographic clouds states, "There is statistical evidence that precipitation from supercooled orographic <br />clouds has been seasonally increased by about 10 %" (adopted by the AMS Council 2 October 1998, <br />Bulletin of the AMS, 72, 57). Stated elsewhere in the policy statement is, "Whereas a statistical <br />evaluation is required to establish that a significant change resulted from a given seeding activity, it must <br />be accompanied by a physical evaluation to confirm that the statistically observed change was due to the <br />seeding." Clearly, the AMS feels that physical measurements and their analysis are an important part of <br />the evaluation of planned weather modification. The World Meteorological Organization (WMO) <br />statement notes that, "In our present state of knowledge, it is considered that the glaciogenic seeding of <br />clouds or cloud systems either formed, or stimulated in development, by air flowing over mountains <br />offers the best prospects for increasing precipitation in an economically viable manner." The AMS and <br />WMO policy statements were prepared by panels of experts. <br />The proposed cloud seeding program has some scientific hurdles to overcome. Most prominent is <br />determining how to best apply the technology to the geographic, and winter weather and cloud conditions <br />of the Headwaters Region. For success, the proposed program must apply state -of -the -art science and <br />technology in conducting the cloud seeding, and executing a proper evaluation of results. Many <br />operational cloud seeding projects seeking additional precipitation seem to eventually become embroiled <br />in controversy as to their accomplishments. Their major problem centers on the inability to determine in. <br />a convincing fashion the seeding effects on precipitation. They suffer from inadequate evaluation design, <br />data collection, and proper analysis. Most cloud seeding projects will eventually need to provide results <br />that can withstand scrutiny from the scientific community. The large area and diversity of the <br />Headwaters Region suggest the proposed project must include a thorough and credible evaluation <br />component that includes statistical evaluation, and selected physical measurements that confirm the <br />seeding of clouds. Prior projects have had great difficulty in ascertaining that clouds actually received <br />treatment. Generally, operational seeding projects attempt to seed all potential cases to maximize results. <br />This approach has complicated (usually negates) determining natural cloud responses in lieu of seeding. <br />