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West Elk Mine 2009 Annual Hydrology Report 5 <br />2.2 Stream Flow Data <br />The North Fork of the Gunnison River (North Fork) and Minnesota Creek are the major <br />surface water resources in the permit area. The U.S. Geological Survey (USGS) maintains gaging <br />stations on both of these streams (USGS 09132500 and USGS 09134000, respectively). Flows in <br />these streams are dominated by snowmelt from upland areas. Flows in WY 2009 in the North Fork <br />of the Gunnison River and Minnesota Creek drainage watersheds were above the historical <br />average. (USGS, 2010a, 2010b, 2010c). <br />2.2.1 Flows in the North Fork of the Gunnison River <br />A summary of the average monthly stream flow data for the North Fork of the Gunnison <br />(North Fork) near Somerset, CO (USGS 09132500; Hydrologic Unit 14020004) including <br />historical and WY 2009 data is graphically presented in Figure 6. Average monthly flows for the <br />North Fork of the Gunnison River near Somerset, CO for WY 2009 ranged from 64.1 cubic feet per <br />second (cfs) (December 2008) to 2,557 cfs (May 2009) (USGS, 2010b). The historical mean <br />monthly flows in the North Fork of the Gunnison River near Somerset, CO collected from WY <br />1934 through WY 2009 have ranged from 66.4 cfs (January) to 1,912 cfs (May) (USGS, 2010b). <br />The average monthly flows in the North Fork of the Gunnison River near Somerset, CO in WY <br />• <br />2009 were above historical means from January through May 2009 and August and September <br />2009, and below historical means from October through December 2008 and June and July 2009 <br />(USGS, 2010b). Flows in the North Fork of the Gunnison are influenced by upstream releases and <br />storage in Overland Reservoir and Paonia Reservoir (since February 1962), small diversions for <br />irrigation in nearby drainage areas, irrigation of about 3,000 acres upstream from station. <br />The mean annual flow for the North Fork in WY 2009 was 531 cfs corresponding to about 116 <br />percent of the historical annual mean for Water Years 1934 through 2009 (456 cfs) (USGS, 2010b). <br />Historical mean annual flows in the North Fork have ranged from 114 cfs in 1977 to 829 cfs in <br />1984 (USGS, 2010b). The peak flow in the North Fork of the Gunnison River in WY 2009 was <br />3,810 cfs on May 7, 2009, compared to the maximum peak flow for the period of record, 9,220 cfs <br />on May 24, 1984 (USGS 2010b). <br />June 2010 HydroGeo, Inc.