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~O ~ : l • Section 2.04.5 General Description of Hydrology and Geology. (1) (a) No information on the surface and ground water systems has been furnished by the Division. (b) Surface Water System. The mine permit area is drained by Sylvester Gulch, an ephemeral stream, directly into the North Fork of the Gunnison River. No flow or water quality information is available for small ephemeral streams. Sylvester Gulch and the other small ephemeral streams in the permit area, all of them located south of the North Fork of the Gunnison River, provide an extremely small portion of the total flow in the North Fork of the Gunnison River. No information on the Sylvester Gulch flow is currently available, so it is not discussed separately from the North Fork of the • Gunnison River. The flow in the North Fork is moderated somewhat by Paonia Reservoir which was filled starting in 1961. From 1967 to 1974 the maximum and minimum flows recorded at the U.S.G.S. gauging station (9-1325) near Somerset were 5100 cfs (cubic feet per second; May 20, 1973) and 40 cfs (January 7, 1968 and January 24, 1969). Mean monthly flows for the 1967 b to 1974 period are presented graphically on Figure 2.04.5(1)(1). Coal Creek and Anthracite Creek join the Plorth Fork of the Gunnison River below Paonia Reservoir. These major tributaries contribute to the wide fluctuation in flow rates in the river despite the moderating influence of the, reservoir. Water in the North Fork of the Gunnison River is a seasonally variable, soft to moderately hard, calcium-magnesium-sodium-bicarbonate type water. The major concentration of the chemical constituents, i.e., calcium, magnesium, sodium and bicarbonate, are negatively correlated with flow (i.e., the greater the flow the less the concentrations of these constituents). Preliminary investigations . during the Fall of 1975 showed that trace element concentrations in the North Fork of the Gunnison River (as well as in ~:innesota 5-1