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conversion factor that converts radiation in langely/d to inches of evaporation <br />• potential per month. Taking an average month to be 30.4 days, C = 0.02053. For <br />example, the January loss from the snow pack is <br />E,N = 0.55 (0.006 (14.8) + 0.05) (215) (0.02053) = 0.34 inches <br />A similar computation was made for each of the months of November through March. <br />Based on The mean monthly temperatures, no snowmelt was assumed for these same <br />months. Therefore, all snow fall, minus the evaporation/sublimation losses, was <br />assumed to accumulate and begin melting in April. These computations are <br />summarized in Table 2.5-20. <br />The precipitation available for infiliraTion or runoff for the months of April <br />and May were computed by assuming the cumulative net snowfall (5.64 inches) rnelTs <br />in April and May. The fraction of the cumulative net snowfall that melts in each <br />of these two months was estimated from the measured runoff hydrographs reported <br />by McWhorter (1979). On This basis it was estimated that 38 percent of the <br />cumulative net snowfall melts in April and The remainder in May. In addition, the <br />snow that falls in these months is assumed to melt in the same month. Therefore, <br />• the snowmelt for April is 3.57 inches and for May is 3.81 inches. These values ore <br />added to the precipitation in the form of rain to obtain the April and May available <br />precipitation values given in Table 2.5-20. <br />Evapotranspiration on the Edna Mine area was estimated from the Jenson- <br />Haise equation as modified by Wymore (1974): <br />Et = Kc L0.014T - (0.57 - 0.04E I )] RSC, <br />where Et is the monthly evapotranspiration, EI is the elevation in thousands of feet, <br />and other symbols are as previously defined. Values of Kc for the growing season <br />are variable and different from the winter season values. The computations are <br />shown in Table 2.5-21. <br />The values of Et in Table 2.5-21 represent the evopotranspirotion that would <br />occur if adequate water were available at all times. Actual evapotranspiration, Eta, <br />will depend upon water availability and is computed as part of the subsurface water <br />budget. Clearly, the actual evaporation over the season will be less the value of Et <br />calculated above, since the seasonal Et is greater Than the available precipitation of <br />• 16.83 inches. <br />2.5-79 <br />