Lyman Dam

About Lyman Dam

The primary purpose of Lyman Dam is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Arizona State Parks;grovers Hill Irrigation District (private). It impounds the Little Colorado River near St. Johns.

The dam stands 60 feet tall and stretches 800 feet across, creates a reservoir covering 1,324 acres, has a maximum storage capacity of 44,500 acre-feet, and collects water from a drainage area of 790 square miles. Completed in 1912, 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 09/05/2024.

At 60 feet, this dam is taller than 95% 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 Arizona dam safety program can provide more specific information about emergency planning for this structure.

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