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West Elk Mine 2012 Annual Hydrology Report 4 <br />Figure 3. Monthly Precipitation Data for Overland Reservoir (59853) <br />Overland Reservoir <br />4 -- - <br />3.5 <br />a 3 <br />a 2.5 <br />e 2 <br />O <br />w <br />:r 1.5 <br />'c. <br />v <br />L <br />a 0.5 <br />0 <br />Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep <br />—* —Total Monthly Precipitation WY 2012 —Average Monthly Precipitation WY 1990 -2011 l <br />Adapted from NRCS (2013b) <br />The snow water equivalent (SWE), a measure of the amount of water in the snow pack, <br />was derived from SNOTEL data recorded at Overland Reservoir and McClure Pass <br />stations (MRCS, 2013c). Historical SWE data for Overland Reservoir are available <br />beginning in WY 1990 and for McClure Pass beginning in WY 1981. A summary of the <br />average monthly SWE data is graphically shown in Figures 4 and 5. In WY 2012, the <br />annual average SWE at Overland Reservoir was 2.74 inches and 2.9 inches at McClure <br />Pass, compared to the historical annual SWE averages of 4.25 inches at Overland <br />Reservoir (WY 1990 -WY 2011) and 5.5 inches at McClure Pass (WY 1981 -WY 2011). <br />These SWE values correspond to 64% of the historical annual average SWE for Overland <br />Reservoir and 54% for McClure Pass. <br />June 2013 H.VdroCeo, Inc. <br />