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<br />W <br />-.J <br />1'< <br />00 <br /> <br />found in western Colorado in the Four Corners area and the G1enwood- <br />Dotsero area, in Arizona near Blue Springs, and in eastern Utah. It <br />is the gypsiferous Mancos Shales in eastern Utah and western Colorado <br />that account for much of the natural salt load of that area. <br /> <br />In hundreds of square miles of the Green River area, there is little <br />soil cover, and bare sandstone and shale are exposed to the elements. <br />Associated with the outcrops are large acreages of shallow soils that <br />are less than a foot deep. The shallow soils are extensive at lower <br />elevations, particularly in the Upper Main Stem and San Juan-Colorado <br />subregions. Soils that are several feet deep are mainly along stream <br />valleys, on old pediment surfaces, and on uplands mantled by wind- <br />deposited or 10essia1 soils. <br /> <br />Critical diffuse salt source areas occur in much of the semiarid to arid <br />portions of the Basin. They are frequently associated with outcrop <br />areas or soils derived from soft shales, siltstones, claystones, and <br />1akebed deposits in valley alluvium. <br /> <br />5. Climate and Air Quality <br /> <br />Climate extremes in the Colorado River Basin range from hot and arid in <br />the desert areas to cold and humid in the mountain ranges. Precipita- <br />tionis largely controlled by elevation and the orographic effects of <br />mountain ranges. Desert areas may receive as little as 3 inches of <br />precipitation annually while high mountain areas may receive more than <br />60 inches. <br /> <br />In the desert areas, temperatures in excess of 100 of are common during <br />much of the summer, while in mountainous areas wi nter temperatures below <br />zero occur regularly. Frost-free periods range from less than 60 days <br />in the high mountains to nearly year long in the desert valleys. <br /> <br />Air quality throughout the Colorado River Basin varies considerably in <br />different locales. Throughout most of the region, air quality is good; <br />but at some areas, particularly close to metropolitan or urban areas, <br />the atmosphere has undergone some degradation. <br /> <br />6. Vegetation <br /> <br />The Colorado River Basin has a wide variety of vegetative cover types <br />ranging from alpine tundra meadow areas on mountain peaks through <br />coniferous forest, pinyon-juniper and oak woodlands, shrub, grassland, <br />and desert communities. Irrigated pasture and cultivated land are <br />scattered throughout the Basin. A listing of common plant species for <br />the Upper Basin and the Lower Basin is presented in appendix A, volume 1 <br />of FES (Final Enviromental Statement) 77-15 [1)* for CRWQIP. <br /> <br />* Numbers in brackets refer to references at end of report. <br /> <br />II-4 <br />