Yellowtail Dam


The Yellowtail Unit in Southcentral Montana is part of the Pick-Sloan Missouri Basin Program. It is a multi-purpose development providing irrigation water, flood control, recreation and power generation. Facilities consist of Yellowtail Dam and Bighorn Lake on the Bighorn River, Yellowtail Powerplant at the toe of the dam, Yellowtail Afterbay Dam--a short distance downstream--and related structures.

The Crow Indian Reservation, spreading over about 3,500 square miles, encompasses the dam site, a portion of the reservoir area. Yellowtail Dam at the mouth of Bighorn Canyon impounds the river for multi-purpose use. Bighorn Lake is about 72 miles long at maximum water surface elevation, 66 miles long at the top of joint-use storage, and extends into the Bighorn basin of Wyoming. The reservoir is confined in the canyon for most of its length.

Madison limestone which due to topographic expression has been divided into three members; lower, middle, and upper. Special treatment: Grouting beneath the dam, grouting in lower, middle, and upper Madison formations of the right and left abutments, supplemental grouting program of the left abutment.

RegionFacilities in Great Plains | Great Plains Home Page
CountyBig Horn
ProjectYellowtail Unit, Pick-Sloan Missouri River Basin Program
Dam TypeConcrete thin arch
ReservoirBighorn River
WatercourseBighorn River
LocationOn Bighorn River, near Fort Smith, Montana in Big Horn County in South-Central Montana, 43 miles southwest of Hardin Montana.
Net Generation510,564,280 kWh
Original Construction1963-1966
Modified Construction
National ID NumberMT00576
Hydrologic Unit Code

Structural Height525.00 ft
Hydraulic Height (Normal Operating Depth at Dam)495.00 ft
Top Parapet (Elevation)3,664.00 ft
Spillway Crest Elevation3,593.00 ft
Crest Elevation3,660.00 ft
Crest Length1,480.00 ft
Crest Width22.00 ft
Base Width147.00 ft
Volume of Dam Construction Materials1,545,664.00 cu yds
Streambed at Dam Axis 3,166.00 ft
Top of Exclusive Flood Control Pool (Elevation) 3,657.00 ft
Top of Joint Use Pool (Elevation)3,640.00 ft
Top of Active Conservation Pool (Elevation)3,614.00 ft
Top of Inactive Conservation Pool (Elevation)3,547.00 ft
Top of Dead Storage Pool (Elevation)3,296.50 ft

Hydraulics & Hydrology
Total Water Storage at Elevation1,381,189.00 acre-ft at 3,660.00 ft
Maximum Water Surface Elevation 1,381,189.00 acre-ft at 3,660.00 ft
Normal Water Surface Elevation
Spillway TypeConcrete tunnel through the left abutment, controlled by two 25- by 64.4- ft radial gates.
Auxiliary Spillway
Spillway Capacity at Elevation92,000.00 cfs at 3,660.00 ft
Auxiliary Spillway Capacity at Elevation
Uncontrolled Spillway Capacity at Elevation
Outlet Works Capacity at Elevation2,500.00 cfs
Diversion Capacity at Elevation
Drainage Area
Hydrometeorological Report (HMR)
Probable Maximum Flood (PMF) Report

Contact Information
TitleArea Manager
OrganizationMontana Area Office
AddressP.O. Box 30137
CityBillings, MT 59107-0137
Phone (Fax)406 247-7338
Phone (Office)406 247-7300
TitleArea Manager
OrganizationMontana Area Office
AddressP.O. Box 30137
CityBillings, MT 59107-0137
Phone (Fax)406 247-7338
Phone (Office)406 247-7300

Last updated: Apr 02, 2013