Angostura Dam (U.S.)

Angostura Dam is an embankment dam across the Cheyenne River in Fall River County in southwestern South Dakota in the United States, about 75 mi south of Rapid City. The dam consists of an earth-fill embankment with a concrete spillway section, 193 ft high and 2030 ft long; it withholds the 195121 acre feet Angostura Reservoir. The dam was conceived as early as 1913, but it was not until the 1930s when a regional drought caused crop failures that the project received widespread support from farmers. Built from 1946 to 1949, the dam is part of the Angostura Division of the Pick-Sloan Missouri Basin Program, and is operated by the U.S. Bureau of Reclamation.

The dam's primary purpose is to store water for the irrigation of 12218 acre of project lands. The service area lies along 24 mi of the Cheyenne River below the dam, and is supplied by the Angostura Canal, which has a diversion capacity of 290 cuft/s. The dam and reservoir regulate runoff from an area of 9034 mi2. The reservoir has a conservation storage capacity of 138761 acre feet, with an extra 56740 acre feet of surcharge, flood-control storage. Flood water releases are controlled by a spillway with five radial gates, which can pass up to 247000 cuft/s.

Angostura Reservoir is one of the only large lakes in western South Dakota. With 36 mi of shoreline and 4706 acre of water, the reservoir is stocked with several species of fish, including walleye, smallmouth bass and crappie.

The Angostura Recreation Area operated by the South Dakota Department of Game, Fish, and Parks surrounds the lake.