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<br />, <br /> <br />~. <br />~ <br />~. <br />~ <br /> <br />Substantial areal variations of sediment and water yields in the Upper <br /> <br />Colorado River Basin were shown to occur by lorns, Hembree, and Oakland (1965) <br /> <br />and Andrews (1979). Sediment yields are relatively small, 10 to 100 tons per <br /> <br />square mile per year in the mountaineous parts of the basin, whereas the water <br /> <br />yields are relatively larger. Conversely, the low-land areas of the Upper <br /> <br />Colorado River Basin have relatively larger sediment yields--500 to 2,000 tons <br /> <br />per square mile per year--and smaller water yields. The basin-wide variation <br /> <br />in sediment yields is the result of several factors--geology, soil-profile <br /> <br />development. topography relief, and precipitation. Due to the areal differ- <br /> <br />ences in sediment yield. the relative impact of land disturbance upon stream <br /> <br />sediment loads varies considerably depending upon location, as shown by <br /> <br />Andrews. (1978). In those parts of the Upper Colorado River Basin that natu- <br /> <br />rally have high sediment yields, land disturbance will not substantially <br /> <br />increase the supply of sediment to the stream channel. In those parts of the <br /> <br />Basin that naturally have low sediment yields, however, land disturbance will <br /> <br />probably significantly increase the supply of sediment to the stream channels. <br /> <br />.~ <br /> <br />y <br />