Lewiston Dam

About Lewiston Dam

The primary purpose of Lewiston Dam is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by Bureau Of Reclamation (federal). It impounds the Trinity River.

The dam stands 91 feet tall and stretches 745 feet across, creates a reservoir covering 750 acres, has a maximum storage capacity of 14,660 acre-feet, and collects water from a drainage area of 718 square miles. Completed in 1963, 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 04/19/2023.

At 91 feet, this dam is taller than 98% 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 California dam safety program can provide more specific information about emergency planning for this structure.

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