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~o- ; <br />'= MJ Y. <br />During the period May through September, the amount of precipitation <br />which falls upon the watershed is less than the potential amount of <br />water lost to evapotranspiration (PET). In other words, transpiration <br />by native vegetation and evaporation consumes most of the precipitation <br />and also will remove water from the soil profile. Far those areas <br />where cash crops such as apples, peaches, and the like are grown, <br />irrigation water is removed from the North Fork of the Gunnison River <br />and applied on such lands. <br />Surface water in the general area is dominated by the North Fork of the <br />Gunnison River. Flow records exist for a U.S.G.S. Gaging Station near <br />Somerset. °Data from this station (Table 2) show inflows to the area <br />and releases from Paonia Reservoir. Outflow from the basin is not as <br />easily determined. For example, the nearest station to Paonia is <br />located on the Gunnison River near Lazear, Colorado, 11 miles southwest <br />of Paonia. Such a station is too far from the study area to be <br />acceptable for this analysis since many inflows and outflows occur <br />between Paonia and Lazear. However, a review of past U.S. Geological <br />Survey (U.S.G.S.) records indicates that for the years 1922 through <br />1932, a gaging station existed on the North Fork of the Gunnison River <br />near Paonia. Also, for the years 1932 through 1950, a gaging station <br />existed in Somerset. These two stations are important since Paonia <br />Reservoir was not yet constructed and, thus,~did not affect inflows to <br />the basin. <br />Use of these stations allows determination of approximate inflows to <br />the North Fork of the Gunnison River contributed by the study watershed <br />boundary located on Figure 1. The average monthly flows are <br />illustrated on Table 2, along with the inflows to the North Fork of the <br />Gunnison River from Minnesota Creek. These figures were used to <br />determine the amount of outflow via the North Fork of the Gunnison <br />River from the basin. Obviously, such predictions are not absolutely <br />accurate. For example, less than 3 years of data existed for Minnesota <br />Creek and 1 year (1977) experienced drought conditions. However, for <br />purposes of this assessment, such figures provide a rough approximation <br />of flows through the general area. <br />PROBABLE HYDROLOGIC CONSEQUENCES <br />Ground Water <br />Since the Mt. Gunnison No. 1 Mine began operations, it has experienced <br />some mine inflows. There are three basic types of mine inflows that <br />are seen at the mine. The first type of inflow is due to primary <br />permeability which is ground-water flow through the competent portions <br />of F-seam and lower Barren Member. The second type of inflow occurs in <br />the coal seam and overlying Barren Member in areas of shallow <br />overburden; this is secondary permeability and is the result of <br />ground-water flow through the fractured and weathered portidns of these <br />strata. The fractured rock acts as a conduit to the surface colluvial <br /> <br />