Yellowtail Dam

About Yellowtail Dam

Yellowtail Dam is a dam in Big Horn, Montana. The dam is owned by Bureau Of Reclamation (federal). It impounds the Bighorn River near Fort Smith.

The dam stands 525 feet tall and stretches 1,480 feet across, creates a reservoir covering 17,958 acres, has a maximum storage capacity of 1,331,725 acre-feet, and collects water from a drainage area of 19,627 square miles. Completed in 1966, the structure is well into its service life at over 50 years old.

This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. An emergency action plan is in place for this dam. The most recent inspection on record was 04/25/2023.

At 525 feet, this dam is taller than 99% of all dams in the United States.

Living Downstream

If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Montana dam safety program can provide more specific information about emergency planning for this structure.

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