Henrys Lake

About Henrys Lake

Henrys Lake is a dam in Fremont, Idaho. The dam is private-owned. It impounds the Henrys Fork Snake River near Macks Inn.

The dam stands 25 feet tall and stretches 408 feet across, creates a reservoir covering 6,050 acres, has a storage capacity of 58,700 acre-feet, and collects water from a drainage area of 93 square miles. Completed in 1923, the structure is over a century 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. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 10/08/2020.

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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