1949 Angostura Dam on Cheyenne River near Hot Springs, SD

(Satellite)

usbr

Angostura dam is a composite type, consisting of a concrete gravity structure and an earth embankment. The concrete portion of the dam comprises a gated spillway section located in the river channel and two non-overflow sections, one extending to the left abutment and one abutting the earth embankment extending to the right abutment. The dam has a crest length of 2,030 feet; the concrete section is 970 feet long and the earth embankment 1,060 feet long, with a structural height of 193 feet and a hydraulic height of 136 feet above the riverbed.

The spillway is an overflow section in the concrete portion of the dam, controlled by five 50- by 30-foot radial gates. Discharge capacity is 247,000 cubic feet per second. The river outlet works consists of a 4.5-foot diameter steel conduit through the concrete dam section, controlled by one 4-foot-square high-pressure slide gate in the valve house at the downstream end. Discharge capacity is 590 cubic feet per second. The main canal outlet works for irrigation water delivery consists of a 6-foot-diameter steel conduit through the concrete dam terminating in a valve house, a stilling basin, and canal headworks at the downstream end. Releases into the 290-cubic- foot-per-second-capacity canal are controlled by two 3.5-foot-square high-pressure slide gates in the valve house.

Bureau of Reclamation posted two photos with the comment:

The Angostura Dam, an embankment dam, spans across the Cheyenne River in Fall River County, located in southwestern South Dakota approximately 75 miles south of Rapid City. Comprising an earth-fill embankment and a concrete spillway section, the dam stands 193 feet high and stretches 2,030 feet long. It retains the Angostura Reservoir, which has a capacity of 195,121 acre-feet of water.

Constructed between 1946 and 1949, the dam is a component of the Angostura Division of the Pick-Sloan Missouri Basin Program and is operated by the Angostura Irrigation District.

The primary function of the dam is to store water for irrigating 12,218 acres of project lands. 

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This would be the outlet and canal for irrigation.

Satellite

ebay, cropped