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2.04.7 Hydrology Description <br />(2) Surface Water Information. <br />(a) and (b) <br />The surface water information is organized in the following categories; 1) <br />Watershed, the river and stream network beginning at the Colorado River; 2) <br />the North Fork of the Gunnison River; 3) streams draining the permit and <br />adjacent area; 4) stockponds within the permit and adjacent area; and 5) <br />surface water on the mine site. <br />Watershed <br />The proposed mine plan and adjacent area lie within the Upper Main Stem of <br />the Upper Colorado River Region in Colorado. The Upper Main Stem is <br />composed of nine major sub - basins: Middle Park, Eagle River, Roaring Fork, <br />Rifle -West Divide, Grand Valley, Upper Gunnison, North Fork, Uncompahgre, <br />and Whitewater. Altitudes range from about 4,300 feet on the Colorado River <br />at the Colorado -Utah state line to over 14,000 feet on the Continental Divide, <br />which forms the eastern margin of the watershed. Only the North Fork may <br />be affected by the Bowie #2 Mine. <br />North Fork of the Gunnison River <br />A USGS gauging station (No. 09132500) is located 2.3 miles east of <br />Somerset and 4.8 miles upstream from Hubbard Creek. The period of record <br />is October 1933 to current year. The gauge is a water -stage recorder with <br />satellite telemetry about 6280 feet above sea level. <br />The average annual discharge of the North Fork of the Gunnison River for <br />the period of record 1934 to 2008 is 330,000 acre feet. At this gauging station <br />there is a drainage area of 526 square miles with an average elevation of <br />8,700 feet. This is a water yield of 627 acre -feet per square mile. During 2007 <br />and 2008 the river discharged at total of 272,400 and 453,600 acre feet <br />respectively. <br />Water flows and water quality in the North Fork are strongly influenced by <br />water control through Overland and Paonia Reservoirs, by water withdrawal <br />from several irrigation canals, and by reflow from irrigated lands back into the <br />river. Withdrawals at Somerset (Fire Mountain Canal), between Bowie and <br />Paonia (Stewart Ditch), and just above Paonia (Farmers Ditch) withdraw <br />significant flows and cause significant dewatering of the river. Some of this <br />water returns to the river near and below Paonia. <br />Irrigation has - significant effects on water volume and quality of the North — - <br />Fork. It contributes to reduced flows and increased salinity, nutrients, and <br />probably herbicide /pesticide levels. Indirectly, lower flows contribute to <br />higher summer temperatures. The municipality of Hotchkiss (below Paonia), <br />PR -12 2.04-40- 02/10 <br />6legow -D <br />/I //6 /fd <br />