Square Lake Dam

About Square Lake Dam

The primary purpose of Square 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 Icicle & Peshastin Irrigation District (public utility). It impounds the Prospect Creek near Leavenworth.

The dam stands 7 feet tall and stretches 104 feet across, creates a reservoir covering 500 acres, has a maximum storage capacity of 913 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1938, 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. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 08/13/2018. That was 7 years ago, which is on the longer end for a high-hazard structure.

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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