Anderson Ranch Dam

About Anderson Ranch Dam

The primary purpose of Anderson Ranch Dam is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is owned by Bureau Of Reclamation (federal). It impounds the South Fork Boise River near Reclamation Village.

The dam stands 456 feet tall and stretches 1,350 feet across, creates a reservoir covering 4,815 acres, has a maximum storage capacity of 474,942 acre-feet, and collects water from a drainage area of 975 square miles. Completed in 1950, the structure is well-established, with more than 75 years of service.

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 07/27/2021.

At 456 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 Idaho dam safety program can provide more specific information about emergency planning for this structure.

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