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valleys, the Rollins sandstone receives little recharge, except in the area under the North Fork of the Gunnison River and its associated alluvial deposits. • Some recharge to the Rollins Sandstone may come indirectly from the percolation of sncwmelt and precipitation downward through faults and fractures. Drill holes which penetrated the Rollins Sandstone near the Orchard Valley Mine were initially dry but slowly recovered over a period of time. This is insufficient to provide a desirable well yield. This indicates that recharge along outcrops and subcrops above the level of the North Fork is insufficient to sustain ground water wells developed in the Rollins. The only domestic use of the water from the Rollins sandstone is from wells along the North Fork near the Hawk's Nest Mines. The water quality elsewhere is considered too saline for domestic use (Prince and Arnow, 1974). DESCRIPTION OF THE SURFACE WATER REGIME The North Fork of the Gunnison River is the major drainage for the general area. Smaller streams in or adjacent to the life-of-mine areas are all tributary to the North Fork. Figure 3 contains the drainage map of the study area with the locations of streams and reservoirs which are described in the following discussion. The North Fork has an average annual streamflow at Somerset of approximately 313,500 acre-feet per year (1962-1979). The flow is regulated by the Paonia Reservoir on Muddy Creek five (5) miles upstream of the town of Somerset. The reservoir became operational in 1962. River yields during that period have ranged from a high of 601,800 acre-feet per year in water year 1984 to a low of 82,270 acre-feet in water year 1977. Flow records for the North Fork of the Gunnison River near Somerset are given in Table 2. Water quality parameters for the North Fork are given in Table 3. As indicated, waters in the North Fork are a calcium bicarbonate type. There are moderate levels of sulfate. Salinity averages less than 100 mg/1. Just below Paonia Reservoir, Muddy Creek and Anthracite Creek join to form the North Fork of the Gunnison River. Anthracite Creek contributes about two-thirds of the flow to the North Fork. Anthracite Creek is a perennial stream with an average annual yield of 157,313 acre-feet for the period of record between July 1977 to October 1980 (U.S.D.I., U.S.G.S., 1980). This corresponds to an average flow rate of 217 cfs. The highest discharge recorded was 4,200 cfs on May 27, 1979. low flows of 12 cfs have been recorded several times during the period of record. The water of Anthracite Creek is an alkaline, moderately hard, calcium-bicarbonate type water with an average total dissolved solids Concentration of 71.6 mg/1; average pH is 7.8. Total suspended Solids average approximately 25 mg/1. Dissolved metal concentrations are low throughout the year, and total metal concentrations are directly related to the total suspended solids concentrations. The Hawk's Nest life-of-mine area is drained by nine ephemeral Streams for which no flow records exist. Two of the gulches have had two water samples collected during 1980; once when they were flowing during snowmelt and once • -9-