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-22- 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, which became operational in 1962. Flows 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. A number of separate drainages have their headwaters in the mine environmental study area. Sylvester Gulch and Lone Pine Gulch are ephemeral streams which drain the northern portion of the area. They flow directly into the North Fork. There are five tributaries which drain into the main flow of Minnesota Creek. Characteristics of the drainages are given in Table 1. No flow was observed in Lone Pine Gulch for a period of years thus, it was omitted from the study. Sylvester Gulch is an ephemeral stream and has a drainage area of 4.25 square miles. It is important to note that the major portion of the surface facilities will be located near this drainage in the valley adjacent to the North Fork. The hydrologic yield of Sylvester Gulch is low compared to the other watersheds. This is due to the fact that it drains a lower elevation area with more gentle slopes. Horse Creek, South Prong, Lick Creek, Dry Fork, and East Fork drain into Minnesota Creek. Their slopes are generally more steep 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 of Sylvester Gulch. There are numerous springs located throughout the permit and life of mine area. Measurements indicate that spring flows generally decrease from a high in the early summer to a low point in the fall. A number of the springs dry up in the winter, indicating that their source is most likely a small localized ground water table. Two reservoirs are located within the life of mine area. Minnesota Reservoir is located on Dry Fork. It has a decreed capacity of 1,285 acre-feet. 'IY~e 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 552 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 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. Water quality data has been collected at several sites throughout the environmental study area. The data indicate that those waters are also the calcium bicarbonate type and relatively low total dissolved solids concentrations.