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of the Interior
The Rapid Valley Project consists of Deerfield Dam and Reservoir, located on Castle Creek, a tributary of Rapid Creek, about 25 miles west of Rapid City, South Dakota. There are various irrigation diversion and supply works in the Rapid Valley Water Conservancy District, and 8,900 acres of privately developed land that are provided supplemental irrigation water from Deerfield Reservoir. The reservoir also provides a supplemental supply of water for Rapid City, including Ellsworth Air Force Base. Fish and wildlife benefits are provided, along with water based recreation opportunities. Pactola Reservoir (Rapid Valley Unit) supplements the supply of stored water available from Deerfield Reservoir. Thus, a full water supply for irrigation and municipal purposes is provided.
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Deerfield Dam, a zoned earthfill structure, has a structural height of 133 feet, a crest length of 825 feet, and a crest width of 35 feet. The side-channel spillway, located in the right abutment, is concrete lined with an uncontrolled crest 190 feet long and a capacity of 16,700 cubic feet per second. The outlet works consist of a 5-foot-diameter concrete conduit through the dam base, extending to a 39-inch-diameter steel pipe contained within a 6.5-foot horseshoe-shaped concrete conduit. The steel pipe has a discharge capacity of 275 cubic feet per second. Small releases for fish and wildlife needs can be made through a 6-inch-diameter pipe which parallels the 39-inch- diameter pipe. The reservoir has a capacity of 15,700 acre-feet and a 414-acre water surface area. Conservation storage is 15,200 acre-feet; dead and inactive storage totals 600 acre-feet.
Deerfield Dam and Reservoir are operated and maintained by the Bureau of Reclamation on a pooled storage basis with Pactola Reservoir, which is located downstream from Deerfield Dam on Rapid Creek.
The area in and around Rapid Valley, except for that served by the Iowa Canal Extension, has had irrigation in some form for many years. Until 1930, there was usually a sufficient flow in Rapid Creek to take care of irrigation needs. After 1930, the water supply became inadequate for full irrigation development. Only those crops that could be grown without full water requirement were planted on most farms, the exception being lands with full water rights.
The Dakota Power Company of Rapid City hired consulting engineers in 1915 and 1928 to investigate the possibilities of irrigation and power development along Rapid Creek. In 1937, the Bureau of Reclamation made investigations and prepared a report which presented plans for storage and related facilities.
The President approved construction of the project in 1939 and funds were allotted from the Interior Department appropriation for 1940. That allotment was withdrawn because of delays in negotiations, and the project was resubmitted for approval as a Water Conservation and Utilization Project and approved by the President in 1940. Both authorizations provided for construction of Pactola Dam. Subsequently, the plan for building Pactola Dam was abandoned in favor of the Deerfield Dam site. The new plan was approved in 1942.
Construction was started on July 7, 1942, by the Farm Security Administration and was later continued by the Civilian Conservation Corps and the Civilian Public Service Camp under the Works Projects Administration during World War II. The facilities were completed by the Bureau of Reclamation in 1947. Minor construction cleanup work, and disposal of excess equipment were accomplished in 1949. Water first became available from Deerfield Reservoir storage on May 1, 1948.
A modification of Deerfield Dam to safely pass a revised inflow design flood was started in 1982. The work includes raising the dam by 38 feet, and the existing spillway will be replaced by a new one.
A supplemental supply of stored water is available to the 8,900 acres of irrigated land within the Rapid Valley Water Conservancy District. The integrated irrigated dryland farms in the district produce corn, alfalfa, small grains, pasture, and livestock. The principal products are used to provide a stable feed supply for stockcow herds and the fattening of cattle.
Municipal water needs for Rapid City, including the Ellsworth Air Force Base, are supplemented with stored water from Deerfield Reservoir.
Outdoor recreation facilities at Deerfield Reservoir include picnic grounds, campgrounds, and fishing access. The recreation areas are administered by the Forest Service. The combined cold- and warm-water fishery at the reservoir is maintained by the South Dakota Department of Wildlife, Parks and Forestry.
For specific information on recreational opportunities click on the name below.