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The soils of the basin are classed with the desert soil groups of <br />the Wyoming Basin. In his discussion of these soils, Hunt (1974) writes: <br />"The surface layer typically contains little organic matter and is cal- <br />careous, for leaching is slight. Subsoils * * * contain a layer enriched <br />with lime and/or gypsum, * * *. Because the Wyoming Basin is semiarid <br />and weathering correspondingly slight, the soil textures and compositions <br />are dominated by the parent materials." <br />There are three basic types of parent material: (1) Coarse-textured <br />older alluvium (water-transported sediments) from the Wind River Moun- <br />tains that has formed coarse-textured soils (sandy) in the northeastern <br />part of the area; (2) sedimentary rocks (sandstone, shale, and siltstone) <br />that have weathered to form mostly shallow soils (thickness 10 to 20 <br />inches) and moderately thick soils (thickness 20 to 40 inches) in the <br />western and eastern parts of the area; and (3) wind-deposited sand that <br />has formed soils in the southern part of the area. Stream channels have <br />formed wetlands, bottom lands, and perpetually wet soils on water- <br />transported sediments (U.S. Bureau of Land Management, 1978, p. 2-3). <br />Climate <br />Precipitation within the basin varies widely. Annual precipitation <br />in the Wind River Mountains is as much as 40 inches, which is mostly snow <br />that accumulates during the winter months. The plains receive as little <br />as 6 inches per year in some areas. The variation in precipitation can <br />be seen in table 2, which shows monthly averages and mean annual values <br />for representative weather stations. Although two of these stations, <br />Rock Springs and Pinedale, are outside the basin, they give an indication <br />of precipitation for the southern (Rock Springs) and northern (Pinedale) <br />parts of the basin. <br />The average distribution of precipitation within the year in the <br />interior of the basin is rather uniform. Almost 40 percent of the annual <br />precipitation at the lower elevations of the basin falls during April, <br />May, and June, when most of the snow is melting in the mountains. <br />Few recorded data are available on intensity of rainfall in the <br />basin, but the available records indicate that the most intense rainfall <br />occurs during the summer months. The foothills probably receive a great- <br />er amount of intense rainfall than the areas at lower elevations. <br />Variations in temperature can be seen in table 3. Monthly and mean <br />annual temperatures at the representative weather stations are shown for <br />the 30-year period, 1941-70. <br />Winds are relatively strong, especially in the plains areas. Wind <br />velocities average about 15 miles per hour during winter and spring and <br />about 8 miles per hour during summer. Strong winds of 30 to 40 miles per <br />hour with stronger gusts sometimes prevail for several days. Wind direc- <br />tion is predominately from the west. <br />10