Angostura Dam


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.

RegionFacilities in Great Plains | Great Plains Home Page
StateSouth Dakota
CountyFall River
ProjectPSMBP - Angostura
Dam Type
Reservoir Angostura
WatercourseCheyenne River
Original Construction1946-1949
Modified Construction
National ID Number SD01099
Hydrologic Unit Code

Structural Height193 ft
Hydraulic Height (Normal Operating Depth at Dam)136 ft
Top Parapet (Elevation)
Spillway Crest Elevation
Crest Elevation3199.0 ft
Crest Length2030 ft
Crest Width10 ft
Base Width230 ft
Volume of Dam Construction Materials850000 cu yd
Streambed at Dam Axis
Top of Exclusive Flood Control Pool (Elevation)
Top of Joint Use Pool (Elevation)
Top of Active Conservation Pool (Elevation)
Top of Inactive Conservation Pool (Elevation)
Top of Dead Storage Pool (Elevation)

Hydraulics & Hydrology
Total Water Storage at Elevation 138761 acre-ft at 3187.2
Maximum Water Surface Elevation 3198.1 ft
Normal Water Surface Elevation
Spillway Type
Auxiliary Spillway
Spillway Capacity at Elevation 247000 cfs at 3198.1
Auxiliary Spillway Capacity at Elevation
Uncontrolled Spillway Capacity at Elevation
Outlet Works Capacity at Elevation 590 cfs at 3198.1
Diversion Capacity at Elevation
Drainage Area 9034 sq mi
Hydrometeorological Report (HMR) HMR 51-52
Probable Maximum Flood (PMF) Report 1983 General All Season Storm

Contact Information
TitleArea Office Manager
OrganizationDakotas Area Office
AddressPO Box 1017
CityBismarck, ND 58501
Phone (Fax)701 250-4326
Phone (Office)701 250-4242
OrganizationAngostura Irrigation District
Address317 First St.
CityOral, SD 57766
Phone (Office)605 424-2331

Last updated: Mar 29, 2013