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• 6 II. GENERAL DESCRIPTION OF HYDROLOGY (2.04.5) 2.1 General The G.E.C. mining operation affects two major drainages: Magpie Creek and Newlin Creek. These drainages lie on tha northeast side of the Net Mountain Range in the San Isabel National Forest (see Figure 1). Fzom Figure 1, the only major surface drainage within the general area is the Arkansas River. Magpie Creek flows into Kerlin Creek just below the study area. Newlin Creek flora into Hardscrabble Creek approximately five miles downstream of the study C area and Hardscrabble Creek then flws into the Arkansas River at Portland, Colorado, (approximately five miles below the confluence of Newlin Creek). r The Arkansas River has a drainage area of approximately 4000 square miles at Portland, Colorado. The Magpie Creek and Newlin Creek drainages, together, make up about 14.6 square miles. The Magpie Creek drainage being studied has a drainage area of approximately 2.4 square miles. Its head waters originate at an elevation of 8700 feet and flow northeast. The average elevation of the Magpie Creek drainage is approx- imately 6500 feet. The terrain is mostly rolling foothills represented by open sandy-loam terraces rand tree and shrub covered ravines. The Newlin Creek drain- ' age area being studied is approximately 12.2 square miles. The Newlin Creek drainage extends higher up into the mountainous regions originating at an ale- ; vation of 10,100 feet and floes generally northeast. The average elevation of the Newlin Czeek drainage is approximately 8000 feet. The terrain ranges from the steep mountainous area near the souzce to rolling foothills at the G.E.C. mine site. Both creeks can be characterized as ephemeral streams with a base '• flow of zero. Thus, the seasonal variation in flow comes as a result of snowpack/snowinelt and/or thunderstorms. The magnitude of the runoff deoends ( on the amount of snowpack/snowmelt and/or the intensity and duration of any l particular thunderstorm.