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-30- The North Fork has an annual streamflow at Somerset of approximately 313,200 acre-feet per year (1933-1982). The flow is regulated by the Paonia Reservoir 5 miles upstream of the town of Somerset, which became operational in 1962. Water yields during that period have ranged from a high of 451,300 acre-feet per year in water year 1962 to a low of 82,270 acre-feet in water year 1977. Flow records for the North Fork of the Gunnison are given in Table 2. Water quality parameters for the North Fork are given in Table 3. As indicated, water in the North Fork is 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. 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.G.S., Water Research Data). This corresponds to an average flow rate of 217 cfs. The highest discharge recorded was 4,200 cfs on May 21, 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. Two of the gulches have had two water samples collected during 1980, once when they were flowing during snowmelt and once during a thunderstorm event. The water is alkaline with an average total dissolved solids concentration of 121 mg/1. Total suspended solids concentrations are low. There are a total of eleven springs and seeps within or adjacent to the Hawk's Nest Mines, three are perennial. The maximum total flow from all springs during the summer of 1982 was 16.085 gpm. The Somerset Mine has mine workings beneath Hubbard, Elk, and Bear Creeks. These streams are perennial, ephemeral and intermittent respectively, and drain directly to the North Fork. Bear Creek is perennial below the Somerset Mine's discharge point, where the stream flow is sustained by the mine discharge. Both the Blue Ribbon and the Somerset mines have surface facilities and underground workings within the Hubbard Creek Drainage Basin. During 1980, Hubbard Creek flows ranged from 3 cfs to 130 cfs with an average flow of 31 cfs. The estimated annual yield for Hubbard Creek was 24,700 acre-feet/year, or 8% of the total flow of the North Fork for the year 1980, measured at Somerset, Colorado. Water quality data for Hubbard Creek are presented in Tables 4a and 4b.