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e . . reaches of Silt Mesa, Water is diverted from the Colorado River using a "rock and brush" diversion structure located approximately 1 mile of the plant. The 7,6 mile-long Silt Pump Canal extends northwest from the pumping plant discharge line, carrying irrigation water to land on the lower part of Silt Mesa, The pumped water is used as a supplemental supply or as a replacement supply, for project land formerly irrigated with water from Harvey Gap, and a small portion, with Colorado River water pumped from the Cactus Valley Ditch, Rifle Gap Dam is located on Rifle Creek and 5.5 miles north of Rifle, Colorado, at a point where the creek cuts through the Grand Hogback. The dam and reservoir was built by the Bureau of Reclamation in 1967 to provide supplemental irrigation water to the existing Farmer's Irrigation Company (FICO) and project lands on Davie Mesa, Existing canals and laterals were used and rehabilitated where necessary, Recreation facilities have been constructed at Rifle Gap Reservoir and some facilities are available at Harvey Gap Reservoir, Rifle Gap Dam is a zoned earthfill structure with a height of 157 ft., a crest length of 1,450 ft" and a volume of 1,768,000 cubic yards of material. The spillway consists of a short approach channel, concrete inlet walls, concrete crest structure, and concrete chute and stilling basin. The outlet works consists of a concrete intake structure, and a 6-foot upstream circular tunnel at the gate chamber with two 2.25 foot-square high- pressure gates, The outlet diverts to a downstream 6-foot-diameter flat-bottom free-flow tunnel. That discharges into the spillway stilling basin. A 7-foot-diameter horseshoe tunnel branches from the gate chamber and contains a 30-inch steel pipe that conveys water to a concrete pipe that in turn discharges into Davie Ditch, With a surface area of 359 acres, Rifle Gap Reservoir has a total capacity of 13,602 acre-feet and an active capacity of 12,168 acre-feet. All of this water is accounted for through the District and senior water rights and instream flows, Hydrology and Water Rights The water supply for the District is comprised of the upper 140 square miles of Rifle Creek and pumping from the Colorado River, Three tributaries, East Rifle, Middle Rifle, and West Rifle Creeks, converge a short distance north of the Grand Hogback to form River Creek. The average elevation of the East Rifle Creek watershed is much higher than that of the other two tributaries, and is underlain by cavernous limestone that permit natural underground storage. The stream is fed principally by a large number of springs with relatively constant flow, The District holds water rights for the Project with decreed uses being irrigation, boating, fish, and recreation, The rights carry an appropriation date of November 20, 1951. Some project water is released directly from Rifle Gap Reservoir into Davie Ditch to supply irrigation water to project lands on Davie Mesa, The majority of reservoir releases are made to meet downstream Rifle Creek diversion rights for non-project lands, These releases allow additional diversions from East Rifle Creek upstream from Rifle Gap Reservoir for Project use, Delivered through the Grass Valley Canal, this exchange water provides a full irrigation supply Silt Water Conservancy District Silt Diversion Project Feasibility Study January 2000 Page 8 of 15