Maui Reservoir 40

About Maui Reservoir 40

The primary purpose of Maui Reservoir 40 is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Mahi Pono Holdings, Llc (private). It impounds the Kalialinui Gulch Offstream near Pukalani.

The dam stands 47 feet tall and stretches 810 feet across, creates a reservoir covering 13 acres, has a maximum storage capacity of 165 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1926, 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 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 07/19/2025.

At 47 feet, this dam is taller than 92% 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 Hawaii dam safety program can provide more specific information about emergency planning for this structure.

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