2013-07-02_REPORT - C1980007 (3)

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West Elk Mine 2012 Annual Hydrology Report 7 The mean annual flow for the North Fork near Somerset in WY 2012 was 182 cfs, corresponding to about 40% of the historical annual mean of 458 cfs for WYs 1934 through 2011 (USGS, 2013c). The historical mean annual flows in the North Fork near Somerset have ranged from 114 cfs in 1977 to 829 cfs in 1984 (USGS, 2012a). The maximum peak flow in the North Fork near Somerset in WY 2012 was 1,110 cfs on April 28, 2012 (USGS, 2013c). Flows in the North Fork of the Gunnison River can be influenced by upstream releases and storage in the Overland and Paonia reservoirs (since February 1962), small diversions for irrigation in nearby drainage areas, and irrigation of about 3,000 acres upstream from the station (USGS, 2013c). 2.2.2 Flows in Minnesota Creek near Paonia, CO A summary of the average monthly stream flow data for the Minnesota Creek near Paonia, CO (USGS 09134000; Hydrologic Unit 14020004) gaging station including historical and WY 2012 data, is graphically presented in Figure 7. The average daily flows in Minnesota Creek near Paonia in WY 2012 ranged from 1.4 cfs (September 2, 3, and 4, 2012) to 39 cfs (May 6 and 7, 2012) (USGS, 2013b). In comparison, historical daily averages have ranged from 1.0 cfs (November 14, 1936) to 340 cfs (May 28, 1993) over the period of record from WY 1937 through WY 1947 and WY 1986 through WY 2011 (USGS, 2013b). The average daily flows in Minnesota Creek near Paonia in WY 2012 were near average from October through March, and well below average from April through September (USGS, 2013b) (Figure 7). Figure 7. Average Daily Stream Flow Data for Minnesota Creek near Paonia, CO (USGS 09134000) 120 100 80 w c 60 E Y r 40 20 0 Minnesota Creek near Paonia, CO Oct I Nov I Dec I Jan I Feb I Mar 1 Apr I May I Jun I Jul I Aug I Sep I A%crage Daily Streamllow WY 2012 Average Daily Streamflow WY 1937 -1947 and 1986 -2011 Adapted Rom USGS (2013b) June 2013 HydroGeo, Inc.