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West Elk Mine 2006 Annual Hydrology Report 5 <br />2.2 Stream Flow Data <br />• <br />The North Fork of the Gunnison River (North Fork) and Minnesota Creek are the major drainages <br />in the Project area. The U.S. Geological Survey (USGS) maintains gauging stations on both of <br />these streams. Flow in these watersheds is dominated by snowmelt from upland areas. Flow in <br />WY 2006 in both watersheds was generally near to slightly below the historical average. <br />Average monthly flows for the North Fork by month for WY 2006 ranged from 52 percent in June <br />to 170 percent in April, compared to historical data collected from 1934 through 2005 (USGS, <br />2007a). The average monthly flow for WY 2006 was 89 percent (406 cubic feet per second (cfs) of <br />the historical daily average for the years 1934 through 2005 (455 cfs). The peak flow in the North <br />Fork was 2,380 cfs on May 23, 2006 (USGS, 2007b). A summary of the average monthly stream <br />flow data for the North Fork is graphically presented in Figure 6. <br />Figure 6. Stream Flow Data for the North Fork of the Gunnison River <br />North Fork of the Gunnison <br />2500 <br />.-. 2000 --- ----- ---- ---- ----- --- ----- ---- --- ----- ---- ---- <br />-~--Average Flow <br />3 1500 --- --- ---- --- <br />- ---- ---- ----- ---- --- WYs 1934-2005 <br />0 <br />~ _ ____----___ -.-Average Flow <br />~ 1000 ---- ---- ---- ----- ---- ---- --- -- <br />~ WY 2006 <br />L <br />~ 500 --- ---- ---- - -- ---- ----- <br />0 <br />o'`°~~~ ~~ec~~~ aJa ~~~~`~~~G.c P~~\ ~a~ ~J~~ ~~~~o'J~~ ~~~c <br />Average monthly flows in Minnesota Creek in WY 2006 were slightly below the annual historical <br />averages from 1937 through 1947 and 1985 through 2005. Average monthly flows for WY 2006, <br />compared to historical data, ranged from 61 percent in March 2006 to 162 percent in October 2006. <br />The average monthly flow for the year for WY 2006 was 95 percent (20.8 cfs) of the historical <br />daily average for the years 1937 through 2005 (22 cfs) (USGS, 2007a). The peak flow in <br />Minnesota Creek was 71 cfs on May 20, 2006 (USGS, 2007b). A summary of the average monthly <br />. stream flow data for Minnesota Creek is graphically presented in Figure 7. <br />December 2007 HydrOGeo, Inc. <br />