2020-08-20_REVISION - C1980007 (36)

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of Raven Creek because of that buffer zone. No further mining is planned in the area. A major contributor to flow in Raven Gulch is Deep Creek, a perennial stream that drains the southeastern part of the permit area. Flows in Deep Creek historically have been in the 0.1 to 0.5 cfs range during most of the year, as indicated by MCC's monitoring data from 2000 through 2005. Springtime flows exceed 30 cfs. Alluvium in the Deep Creek watershed is too thin to serve as a ground water supply source. Most of the southern part of the permit area is in the Minnesota Creek watershed that was approved for mining in PR-10. This major watershed covers approximately 53.5 square miles. Tributaries to the mainstem of Minnesota Creek include Horse Creek, South Prong, Lick Creek, Dry Fork, and East Fork. The mainstem of Minnesota Creek enters the North Fork of the Gunnison near the town of Paonia. Based on streamflows measured in water year 1978, prior to mining, the water yields from these drainages are nearly an order of magnitude greater than the yield from Sylvester Gulch. The evaluation of flow within the Minnesota Creek drainage is considered only an approximation due to infiltration and seepage losses, seasonal variations in precipitation and potential evaporation and sampling difficulties. MCC estimates that more than 80% of the South of Divide mining area is in the Dry Fork drainage. MCC also describes the Dry Fork drainage as having minimal yield, but its stream channel annually conveys approximately 720 acre-feet of water imported from Little Gunnison Creek via the Deep Creek Ditch(based on Office of the State Engineer records for 1970 through 2002). The average annual flow of the East Fork of Minnesota Creek is approximately 19,920 acre-feet. Irrigation ditches annually remove about 20,000 acre-feet from Minnesota Creek. Two reservoirs are located in the Minnesota Creek drainage. Minnesota Reservoir is located on the Dry Fork. It has a decreed capacity of 1,285 acre-feet. 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 have been collected at several sites throughout the Minnesota Creek and Deep Creek drainages. The data indicate that these waters are of a sodium-bicarbonate type with relatively low total dissolved solids concentration. Minnesota Reservoir appears to have an effect on the water quality characteristics of Dry Fork. Detention of Dry Fork flows in the 41