Shadehill Dam

Shadehill Dam is a dam (constructed 1951) on the Grand River in Perkins County in northwestern South Dakota in the United States, about 10 mi south of Lemmon. The dam and its impoundment, Shadehill Reservoir, serve mainly for flood and silt control, wildlife conservation and recreation. Located directly below the confluence of the North and South Forks of the Grand River, the dam is operated by the U.S. Bureau of Reclamation, and is part of the Shadehill Unit of the Pick-Sloan Missouri Basin Program.

The dam is an embankment structure 145 ft high and 12843 ft long, with an elevation of 2318 ft at the crest. A catchment area of 3120 mi2 lies above the dam site. At full pool, the reservoir has a capacity of 468585 acre feet, with a surface area of 12150 acre. Normal conservation water levels are much lower, at 81443 acre feet. Regular water discharges pass through an outlet works with a capacity of 600 cuft/s, while flood flows are released through two spillways: a morning glory inlet with a capacity of 5700 cuft/s, and an emergency overflow channel that can pass up to 127000 cuft/s.

Shadehill Dam was originally intended to serve irrigation purposes as well, but after determining that the water in the reservoir was too saline the Bureau of Reclamation dropped this phase from the project.