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-29- are given in Table 5. No flow was observed in Lone Pine Gulch for a period of several years. Sylvester Gulch is an ephemeral stream and has a drainage area of 4.25 square miles. As indicated on Table 5, the hydrologic yield of Sylvester Gulch is low compared to the other watersheds. This is due to the fact that it drains an area which is lower in elevation and which has gentler slopes. The Mt. Gunnison life-of-mine area is drained by five tributaries to Minnesota Creek. East Fork, Horse Creek, South Prong, Lick Creek, and Dry Fork drain into Minnesota Creek from areas to be undermined by the Mt. Gunnison No. 1 Mine. Their slopes are generally steeper and the watersheds are at higher elevations than those tributary to the North Fork. Based upon streamflows measured in water year 1978, the water yields from these drainages are nearly an order of magnitude greater than that from Sylvester Gulch. Two reservoirs are located within the Minnesota Creek drainage. Minnesota Reservoir is located on Dry Fork. It has a decreed capacity of 1,285 acre-feet. The actual capacity may be closer to 500 acre-feet, however. Beaver Reservoir is located on the East Fork of Minnesota Creek and has an absolute decreed capacity of 1,620 acre-feet and a conditional decree of 522 acre-feet. Both reservoirs store water for irrigation purposes and are filled during spring runoff. They are usually drained by late August or early September. Water quality data has been collected at several sites throughout the Minnesota Creek drainage. The data indicate that these waters are of a calcium bicarbonate type with relatively low total dissolved solids concentration. There are over 100 springs located throughout the Mt. Gunnison life-of-mine area. Measurements indicate that spring flows generally decrease from a high in the early summer to a low in the fall. A number of the springs are ephemeral, indicating that their sources are small localized aquifers (i.e. landslide deposits, colluvium, lenticular sandstones, etc.). Precipitation and Runoff Only two precipitation stations exist for the watershed, one at Paonia and one at the Mt. Gunnison mine. Since these are located near the North Fork of the Gunnison River, they may not be representative of the - total watershed. Isohyetal lines can be used to show average precipitation that falls on the watershed. Figure 5 represents mean annual precipitation and Figure 6 illustrates May to September precipitation of the years 1931 to 1960. All values were obtained from maps drawn by the U.S. Weather Bureau. Table 6 summarizes precipitation data for both the north and south sections of the watershed. Comparing.these isohyetal maps with Figure 7 shows that precipitation patterns are strongly influenced by topography.