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required. One of the most promising new sources of water is by <br />precipitation enhancement through cloud seeding to augment the mountain <br />snowpack that feeds the river and its reservoir system. Most of the <br />flow within the Colorado River Basin originates from seasonal snowpack <br />in the alpine and subalpine watersheds where winter precipitation <br />amounts are high and evapotranspiration losses are low due to <br />cold temperatures. Enhancement of the winter precipitation in the <br />context of a total water management system for the Basin offers a <br />unique opportunity to augment both the quantity and quality of water <br />in the river system. Consequently, the Bureau of Reclamation is planning <br />to accelerate its snowpack augmentation project for the Colorado River <br />region to help alleviate anticipated water shortages in the Basin. The <br />program, called the Colorado River Enhanced Snowpack Test (CREST), <br />is designed to demonstrate the technology and quantify the potential water <br />increases from a full basin-operational program. <br />2. Program Rationale <br />The technology of modifying wintertime orographic cloud systems to increase <br />mountain snowpack has been developing over the past 30 years. Both <br />research and operational projects have contributed to a better understanding <br />of weather modification. The accumulated evidence is that seeding under <br />favorable conditions should increase seasonal precipitation 10 to 15 per- <br />cent. Evidence about the potential for wintertime orographic snowpack <br />augmentation in the high mountains of the Colorado River Basin is largely <br />based on statistical data from past projects such as the Climax and Wolf <br />Creek Pass experiments conducted by Colorado State University and the <br />Bureau's Colorado River Basin Pilot Project. These results were consistent <br />with the physical hypothesis that seeding under favorable conditions <br />increases the precipitation efficiency of the cloud systems. In addition, <br />we have gained considerable physical insight into the seedability of <br />orographic cloud systems through the Bureau's Sierra Cooperative Pilot <br />Project and Colorado State University's Colorado Orographic Seeding <br />Experiment. The design of the CREST program is based on this body of <br />statistical and physical knowledge and experience. <br />2 <br />