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2.5.2.6 rologic Emygy~y~;,.r+ <br />• The analysis of the hydrologic balance is restricted to the proposed mine area. <br />The water balance is analyzed on an average annual basis using long term mean data <br />where available. The approach is to break the overall hydrologic balance into two <br />subsystems; a surface water budget and a subsurface water budget. Components <br />considered in The surface water balance ore available precipitation, overland runoff <br />and infiltration. The subsurface balance includes infiltration, soil-water storage, <br />evapotranspiration and subsurface runoff (deep percolation). The two subsystems are <br />linked by infiltration. The basic procedures are described in detail by McWhorter <br />(I 980). <br />Climatic Summary - Table 2.5-3, presented in Section 2.5.2.1 as part of <br />the hydrologic setting, contains the precipitation, temperature, and solar radiation <br />data utilized in The computations. With the exception of solar radiation, the data <br />are 20 year means. <br />Of all stations with long term records, it was judged that the data from the <br />Pyramid, Colorado station most nearly approximates the precipitation on the Edna <br />• Mine. Temperature records were not available at the the Pyramid station, however, <br />and the Temperature records at Steamboat Springs were used. The mean <br />temperatures in Table 2.5-3 are probably somewhat greater than those at the mine <br />site, therefore. <br />Solar radiation data are collected at only a few sites in Colorado. The Fort <br />Collins station is about the same latitiude as the mine site, and therefore, solar <br />radiation from Fort Collins was selected for use. <br />Roia~~(IDgns~r~r,~~U~n - Water loss to the atmosphere was <br />calculated by dividing the year into a winter period and a growing season. The <br />winter period losses result from evaporation and sublimination and were estimated <br />using the equations developed by Wymore (1974) specifically for The western Colorado <br />area. The winter season losses were calculated by month from <br />Kc (0.006 T + 0.05) Rs C, <br />where T = mean Temperature for the month, Rs is the monthly solar radiation <br />expressed in langely per day, and Kc is a cover factor estimated by Wymore to be <br />• equal to 0.55 fora mixture of mountain shrubs and sagebrush. The constant C is o <br />2.5-78 <br /> <br />