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<br />. <br /> <br />PART II <br /> <br />DESCRIPTION OF BASIN <br /> <br />.... <br />C.iT <br />o <br /> <br />Residual soils are usually shallow in depth over shale and sandstone <br />of various ages. !'>tany of the shales are saline but contain gypsum as <br />10'121188 other chloride, sulfate, and bicarbonate salts. ~uch of the salt <br />pickup occurs in areas ...nere the natural runoff contacts the saline <br />shales before entering the streams. Very fe\'" residual soil areas are <br />suitable for icrigat ion development. <br /> <br />- <br /> <br />Alluvial materials vary. ranging from alluvial fans, terraces, and <br />outwash plains to lake sediments. Some soils are composed of material <br />transported only short distances, while other soils have been transported <br />and mixed well. Since most of the agricultural areas are on these well <br />mixed alluviums, cultivated soils vary in composition. <br /> <br />Extensive areas of Eolian deposits (wind arranged, such as sand <br />dunes) occur in part of the basin. The uniformly textured soils are <br />reddish-brown in color and resemble either the underlying formations or <br />adjacent areas. These art' excellent agricultural soils, but in many <br />areas topography makes farming difficult. <br /> <br />E. Vegetat ion <br /> <br />. <br /> <br />Areas of higher elevation are covered with forests of pine, fir, <br />spruce, and aspens, broken by small glades and mountain meadows. Pinyon <br />and juniper trees, interspersed with scrub oak, mountain mahogany, <br />rabbitbrush, bunch grasses, and similar plants grow in the intermediate <br />elevations of the mesa and plateau regions. Large areas in the Upper <br />Basin are dominated by sagebrush-related vegetation, while many of the <br />streams are bordered by cottonwood, willows, and salt cedar. Scattered <br />Cottonwoods and chokecherries grow in the canyons with cliff rose, <br />redbud, and blue columbine, while wildflowers carpet many mountain <br />parks. At lOlo'er elevations large areas have a low density of plant <br />cover with scattered desert shrubs, Joshua trees, other yucca plants, and <br />saguaro cacti, some of which reach 40 feet in height. Occasionally, <br />Cottonwoods or desert willows are found along desert streams with <br />mesquite and creosote bush or cate law and palovercle. Many river flood <br />plains have been so overrun with tamarisk (salt-cedar) that a large <br />volume of water is being consumed by the phreatophyte vegetation. <br /> <br />. <br /> <br />9 <br />