2009-07-01_REPORT - C1980007 (6)

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West Elk Mine 2008 Annual Hydrology Report 5 2.2 Stream Flow Data The North Fork of the Gunnison River (North Fork) and Minnesota Creek are the major surface water resources in the permit area. The U.S. Geological Survey (USGS) maintains gaging stations on both of these streams. Flows in these streams are dominated by snowmelt from upland areas. Flows in WY 2008 in both of the major drainage watersheds in the permit area were generally above the historical average (USGS, 2009a; USGS 2009b). 2.2.1 Flows in the North Fork of the Gunnison River A summary of the average monthly stream flow data for the North Fork of the Gunnison (North Fork) near Somerset, CO including historical and WY 2008 data is graphically presented in Figure 6. Average monthly flows for the North Fork of the Gunnison River near Somerset, CO (USGS 09132500) for WY 2008 ranged from 75.6 cubic feet per second (cfs) (February 2008) to 2,582 cfs (May 2008) (USGS, 2009b). The historical mean monthly flows in the North Fork of the Gunnison River near Somerset, CO collected from WY 1934 through WY 2008 have ranged from 66.0 cfs (January) to 1,903 cfs (May) (USGS, 2009b). The average monthly flows in the North Fork of the Gunnison River near Somerset, CO in WY 2008 were above historical means for all 12 months of WY 2008 (USGS, 2009b). Flows in the North Fork of the Gunnison are influenced by upstream releases from Paonia Reservoir. The mean annual flow for the North Fork in WY 2008 was 625 cfs corresponding to 137 percent of the historical annual mean for Water Years 1934 through 2008 (455 cfs) (USGS, 2009b). Historical mean annual flows in the North Fork have ranged from 114 cfs in 1977 to 829 cfs in 1984 (USGS, 2009b). The peak flow in the North Fork of the Gunnison River in WY 2008 was 4,590 cfs on May 21, 2008, compared to the maximum peak flow of 9,220 cfs on May 24, 1984 (USGS 2009b). 2.2.2 Flows in Minnesota Creek near Paonia, CO A summary of the average monthly stream flow data for Minnesota Creek near Paonia, CO including historical and WY 2008 data is graphically presented in Figure 7. The average monthly flows in Minnesota Creek near Paonia, CO (USGS 09134000) in WY 2008 ranged from 3.87 cfs (February 2008) to 110.4 cfs (June 2008) (USGS NWIS, 2009a). In comparison, historical monthly averages for the period of record have ranged from 3.5 cfs (January) to 87 cfs (May) over the period of record from 1937 through 1947 and 1986 through WY 2008 (USGS NWIS, 2009a). The mean annual flow in Minnesota Creek near Paonia, CO in WY 2008 was 28.7 cfs corresponding to about 132 percent of the historical mean annual flow (21.8 cfs) over the period of record (USGS NWIS, 2009a). The peak flow in Minnesota Creek in WY 2008 was 269 cfs on June 2009 HydroGeo, Inc.