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<br />O~1547 <br /> <br />PROJECT SETTING <br /> <br />Location and Size <br /> <br />The Highline Breaks Watershed is located in eastern Pueblo and Otero counties in <br />southeastern Colorado. The watershed consists of 89,650 acres and averages about <br />4 to 5 miles wide and 35 miles long. La Junta, Colorado, is on the east edge of the <br />watershed and Boone is near the west edge. Pueblo, Colorado, is 20 miles west of <br />the watershed area. <br /> <br />The watershed is bounded on the west by the Highline Canal Diversion, on the south <br />by the Highline and Otero Canals, on the east by the King Arroyo, and on the north by <br />the Arkansas River. It includes the outlet area of the Apishapa River, the Chicosa and <br />Timpas Creeks, the Crooked and Smith Arroyos, and the Patterson Hollow which <br />outlet into the Arkansas River. <br /> <br />Topoaraphyand Drainaae <br /> <br />The highest elevation in the watershed is the Highline Canal. It varies from an <br />elevation of 4,'450 ft. on the west edge of the watershed to 4,050 ft. on the east edge. <br />The Arkansas River or the northern boundary is the lowest elevation in the watershed. <br />The entire watershed area is gently sloping as it drains toward the Arkansas River. <br />John Martin Reservoir is approximately 25 miles downstream of our watershed. John <br />Martin Reservoir is used for flood control, recreation, and irrigation storage. <br /> <br />Geolooy and Physio~raphic DescriptionIl <br /> <br />Highline Breaks watershed is located within the Colorado Piedmont section of the <br />Great Plains Physiographic Province (Fenneman, 1931). The Colorado Piedmont <br />represents an old erosion surface. It is a mature to old, broadly rolling, elevated plain <br />with local scarps. <br /> <br />Bedrock consists primarily of Cretaceous marine shales and limestones. These <br />formations dip slightly to the northwest, toward the Denver structural basin. The <br />oldest formation that crops out in the watershed is the Upper Cretaceous Carlile shale, <br />which is found south of the Arkansas River at La Junta. Overlying the Carlile Shale <br />from oldest to youngest is the Fort Hays limestone and Smokey Hill shale members of <br />the Niobrara Formation and the Pierre shale. <br /> <br />Shales and limestones have higher concentration of some minerals than other rock <br />types. This is particularly true of minerals such as sulfur and trace minerals such as <br />arsenic, boron, and selenium (Turekina and Wedepohl, 1961). <br /> <br />lCht<k In reference wctlon for geology repor1lll for tMlI.retL <br /> <br />10 <br />