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man-made depression just upstream of the road crossing collects runoff in this • area. This unnamed tributary has an earth stock dam across the channel in the upper watershed, The embankment and downstream channel are well vegetated and stabilized at the upper site, 2.0 Characterization of Pryor Canyon Watershed and Channel The drainage area of Pryor Canyon, measured at its confluence with Santa Clara Creek, is 2.57 square miles. Elevation ranges from 7262 feet above MSL at the upper divide to 6355 at the confluence. Climate is semi-arid, with mean annual temperature approximately 52°F, The watershed above the disturbed area has very dense tree cover including fir, pine, and scrub oak, Ground cover is medium, including tall and short grasses, thistle, and small bushes. Watershed side slopes are moderate, averaging about fifteen percent. The soil is a silty clay and infiltration rates are low to medium. Because the silty clay material in which the channels are cut has cohesive properties, the channels are relatively narrow (Figure 2.04.7(2)-1). The channel sides are nearly vertical in most places, Bed material ranges in • size from fine sand to large (2 - 3 foot diameter) rocks. Width of the active channel in the main channel is fifteen to twenty feet, The Raton Formation outcrops approximately one-half mile upstream of the section line, 3.0 Determination of Runoff Peaks and Runoff Volumes for Pryor Mine Four methods of hydrologic analysis have been used to calculate peak flows for the Pryor Canyon drainage basin upstream of the point where the channel enters the permit area. The results are compared and used to estimate runoff at twelve points of interest on the Pryor Mine permit area, The first method is a regression analysis developed for the Arkansas River Basin (U,S.G,S., 1981). This regression analysis can be used to estimate peak flows and the corresponding runoff volumes for the 10-year, 25-year, and 100-year recurrence intervals. The second method is another regression developed for the plains region of Colorado (Colo. Water Cons, Board, 1976). This method can be used to estimate peak flows for the 10-year, 50-year, and 100-year recurrence intervals, The third method is a • JFSA-34 ~ ~~~ 134 y ~ saia & nss~a~s. uric.