Laserfiche WebLink
<br />. <br /> <br />. <br /> <br />The San Miguel River also contributes substantially to <br />the salinity of the Dolores River. Its salt load has been calcu- <br />lated at 544 tons per day. <br /> <br />The sediment discharged by the Dolores River comes mainly <br /> <br /> <br />from lands underlain by marine shales in the more arid parts of <br /> <br /> <br />the basin. High water yield and high sediment yield are often <br /> <br /> <br />derived from different parts of a drainage basin, and the Dolores <br /> <br /> <br />is no exception. The higher elevations in the basin, above the <br /> <br /> <br />town of Dolores, yield an average of 641 acre-feet per square <br /> <br /> <br />mile of drainage area annually, while the sediment load of the <br /> <br /> <br />Dolores at Dolores is 214 tons per square mile. The drainage <br /> <br /> <br />area between Dolores and the mouth of the other hand yields only <br /> <br /> <br />80 acre-feet of runoff per square mile per year while 590 tons <br /> <br /> <br />of sediment per square mile per year reaches the Dolores <br /> <br /> <br />(Figure 1). <br /> <br />The erosion potential of the lands between Dolores and the <br /> <br /> <br />mouth is classified as moderately high to high. _/ Two percent <br /> <br /> <br />of the basin is in cropland, and 68 percent is used by grazing <br /> <br /> <br />livestock. Most of the sediment yield to the river must be <br /> <br /> <br />attributed to normal geologic erosion, however, cropping and <br /> <br /> <br />grazing livestock contribute a small but unmeasured increase <br /> <br /> <br />in the rate of erosion. <br /> <br />Summary and recommendations <br /> <br />The water of the Dolores River above Rico and the West <br /> <br /> <br />Dolores are of good quality. They currently meet existing state <br /> <br /> <br />water quality standards and are expected to continue to do so. <br /> <br />-5- <br /> <br />o~o <br />