2009-02-10_PERMIT FILE - C1981022 (5)

Home Browse Search

Scoria: - 2.04.7 North Fork of the Gunnison River - The North Fork drains an area of approximately 1,250 square • miles, including the entire mine permit and adjacent areas. The headwaters of the North Fork are in the Elk Mountains to the east of the Town of Somerset. The North Fork begins approximately six miles east of Somerset where Anthracite Creek, Coal Creek, Deep Creek, and Muddy Creek join together below Paonia Reservoir. Major tributaries to the North Fork include the following: • Muddy Creek • Deep Creek • Anthracite Creek • Coal Creek • Thompson Creek • Hubbard Creek • Terror Creek • Minnesota Creek • Reynolds Creek • Jay Creek • Cottonwood Creek The North Fork flows to the southwest for approximately 30 miles, where it joins the Gunnison River southwest of the Town of Hotchkiss. The Gunnison River is, in turn, tributary to the Colorado River. Elevations within the North Fork watershed range from approximately 12,000 feet for the mountains to the east and south to 5,000 feet where it joins the Gunnison River. Total average annual discharge of the North Fork is approximately 470,000 acre-feet, corresponding to a discharge rate of approximately 650 cfs (USDA, 1962). The average annual discharge measured over a period of 60 years (1934 to 1994) at a USGS gauging station located approximately 2.3 miles east of the Town of Somerset is 330,500 acre-feet, corresponding to a rate of approximately 450 cfs. The Colorado Division of Water Resources has indicated that discharges from Paonia Reservoir will be used to maintain minimum in-stream flows in the North Fork of 60 cfs. Variations in flow in the North Fork are graphically illustrated by Figures 2.04.7-F9A and 2.04-F9B, Surface Water Flow Hydrographs - North Fork of the Gunnison River Perennial Drainages - Within the mine permit and adjacent areas, the only perennial drainage other than the North Fork is Hubbard Creek, which drains an area of approximately 19 square miles including the extreme western portion of the mine permit area. The headwaters of Hubbard Creek are on the south slope of Grand Mesa approximately 12 miles north of the point where Hubbard Creek joins the North Fork Dove Gulch, Sheep Corral Gulch, Freeman Gulch, and a number of smaller unnamed ephemeral drainages are tributary to Hubbard Creek Hubbard Creek flows to the southeast and joins the North Fork between the Towns of Somerset and Bowie near Juanita Junction. Elevations in the Hubbard Creek watershed range from approximately 10,000 feet near its headwaters to 5,800 feet where it joins the North Fork A peak flow, estimated at 600cfs, was documented for Hubbard Creek in 1984. Nonnal flows range from minimal flow up to approximately 80cfs, with high flows in the spring due to snowmen runoff. During much of the year, typical flows are in the range of 5 to 20 cfs as illustrated by Figures 2.04.7-F10A and 2.04-F10B, Surface Water Flow Hydrographs - Hubbard Creek Intermittent and Ephemeral Drainages - As previously noted, most of the drainages in the area exhibit an intermittent or ephemeral flow pattern, with flow only in response to snowmen runoff or major thunderstorms. While numerous small ephemeral drainages exist in the area, those intermittent or ephemeral drainages which either carry significant flows or would potentially be impacted by mining • operations are limited to (from east to west) Thompson Creek Hawk's Nest Creek Sanborn Creek Elk Creek, and Bear Creek The following summarizes drainage characteristics for these drainages and seasonal flow variations are graphically illustrated by Figures 2.04.7-F11A through 2.04.7-F11I, Surface Water Flow Hydrographs - Intermittent and Ephemeral Drainages: PR04 2.04-54 Revised August 2000