Patterson Lake Dam

About Patterson Lake Dam

The primary purpose of Patterson Lake Dam is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Wolf Creek Reclamation District (public utility). It impounds the Rader Creek near Winthrop.

The dam stands 32 feet tall and stretches 260 feet across, creates a reservoir covering 150 acres, has a maximum storage capacity of 4,100 acre-feet, and collects water from a drainage area of 6 square miles. Completed in 1924, 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. Notably, no emergency action plan is currently on file for this high-hazard dam. The most recent inspection on record was 10/18/2021.

At 32 feet, this dam is taller than 76% of dams nationwide.

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 Washington dam safety program can provide more specific information about emergency planning for this structure.

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