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<br />INTRODUCTION <br />This report describes a prototype automated precipitation enhancement system <br />(APES) constructed during the summer/fall, 1993, to seed winter orographic <br />(mountain-induced) clouds. The system is designed to automatically dispense <br />liquid propane at high elevation during appropriate winter storms. This work <br />relies heavily on the seminal work of David Reynolds (D-3720) working with the <br />California Division of Water Resources (Reynolds, 1989 and 1991). The <br />research described in this report was funded through Reclamation's WATER <br />program and cost shared by Emery Water Conservancy District (WCD) and the Utah <br />Division of Water Resources. <br /> <br />CAVEAT <br />The system described in this report is untested and the following information <br />is provided only as a progress report. <br /> <br />The information contained in this report regarding commercial products or <br /> <br /> <br />firms may not be used for advertising or promotional purposes and is not to be <br /> <br />construed as an endorsement of any product or firm by the Bureau of <br /> <br />Reclamation. <br /> <br />RESEARCH OBJECTIVES <br />Research into precipitation enhancement has shown that the effectiveness of <br />the Utah operational winter cloud seeding program can be improved by seeding <br />with propane during periods when supercooled liquid water clouds are too warm <br />for nucleation of ice crystals with silver iodide, the agent currently used. <br />This requires that propane dispensers be operated at high elevations, well up <br />the windward slopes of mountain barriers, within the cloudy air at <br />temperatures below ooC. <br /> <br />A second improvement relates to the use of forecasting to initiate and <br /> <br /> <br />terminate cloud seeding. Weather forecasting is especially difficult for <br /> <br />2 <br />