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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Executive Summary <br /> <br />In agreement with the Division of Water Resources, State of Utah, the climatology of winter storms <br />in the Uinta Basin and along the Wasatch Front was investigated. The purpose of the study was to <br />evaluate Utah terrain and its effect on orographic precipitation patterns. <br /> <br />The 1951-1980 normal precipitation calculations show that on the average, the Uinta Basin receives <br />about 8 inches of precipitation annually. About half of the precipitation results from winter storms. <br />At higher elevations, about three-quarters of all precipitation comes from winter storms. Because <br />much of the precipitation at higher elevations in winter storms falls as snow, it becomes available <br />as runoff in the spring and summer months and is therefore valuable to residents in the Basin for <br />irrigation and other purposes. <br /> <br />This study presents the climatology of Utah and the Uinta Basin. Winter and spring storms were <br />classified into four categories. The first represents a ridge position over the intermountain west and <br />allows very little precipitation to be produced in the Utah area. The additional three categories <br />reflect wind flow from the northwest, the southwest and the southeast. These studies show most <br />storms which produce significant precipitation in the Basin come from the southwest through <br />southeast. Relatively few storms from the west or northwest result in precipitation in the Basin. <br />This climatology of storms was verified using correlations among precipitation stations and by <br />modelling storm wind trajectories and precipitation patterns. <br /> <br /> <br />During periods of drought in the Basin, there is always concern about water availability for municipal <br />and industrial systems and for irrigation. To show historical periods of water deficit or drought in <br />the Basin and their relation vlith other areas, long-term meteorological drought indices are <br />presented. Emphasis is placed on the last ten years of record. The present severity of drought in <br />the Basin is presented and related directly to past droughts and drought severity in other areas of <br />the State. <br /> <br />The Rhea orographic precipitation model was used to evaluate the effect of winter storms and their <br />precipitation distribution patterns in the Basin. The model was calibrated to 1984 winter and spring <br />storms. Results verify that much of the precipitation in the Uinta Basin results from storms from <br />the southerly directions. <br /> <br />II <br />