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Mountain Coal Company 1999 Annual Hydrology Report Wes! Elk Mine <br />• percent of the average at the Overland Reservoir station. Figures 1 through 3 show the monthly <br />distribution of the precipitation measured at each of these three stations. <br />Hydrological Data <br />)n addition to the climatological data, a water year can be chazacterized by streamflow. The <br />major drainage basins in the vicinity of the West Elk Mine aze the North Fork of the Gunnison <br />River (North Fork) and Minnesota Creek. The U.S. Geological Survey (USGS) has gaging <br />stations on both of these streams. Both of these watersheds aze lazge and the annual flow is <br />dominated by snowmelt from the higher elevations. The North Fork flow regime is also affected <br />by Paonia Reservoir. <br />To facilitate comparison of the WY99 streamflow data to the period of record, Figures 4 and 5 <br />were prepazed. These graphs indicate that flows in both the North Fork drainage and in <br />Minnesota Creek were well below average, primarily due to the below average snowpack noted <br />above. <br />Annual runoff in the North Fork drainage was 78% of the long-term average, and in the <br />Minnesota Creek drainage, runoff was only 51% of the long-term average. For WY99, an <br />instantaneous peak discharge of 2,650 cubic feet per second (cfs) was recorded on the North <br />Fork on May 23, and an instantaneous peak discharge of 89 cfs was recorded on Minnesota <br />Creek on June 8. <br />• <br />r 1 <br />U <br />83l-031.510 Paget Wright Warer Engineers <br />