Omao Reservoir
Omao Reservoir is an earth dam located in Kauai County, Hawaii, built in 1915. It carries a High hazard potential classification and has a unsatisfactory condition assessment.
About Omao Reservoir
The primary purpose of Omao Reservoir is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Alexander & Baldwin, Inc., Eric A. Knudsen Trust (private). It impounds the Omao Stream near Koloa.
The dam stands 32 feet tall and stretches 454 feet across, creates a reservoir covering 8 acres, has a maximum storage capacity of 194 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1915, 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 unsatisfactory, indicating serious safety deficiencies exist that require immediate attention or remedial action. An emergency action plan is in place for this dam. The most recent inspection on record was 03/06/2025.
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 Hawaii dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Hawaii |
| County | Kauai |
| Nearest City | Koloa |
| River/Stream | Omao Stream |
| Coordinates | 21.92112, -159.48321 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 32 ft |
| Dam Height | 32 ft |
| Dam Length | 454 ft |
| Year Completed | 1915 (111 years old) |
Storage & Hydraulics
| NID Storage | 194 acre-ft |
| Max Storage | 194 acre-ft |
| Normal Storage | 139 acre-ft |
| Surface Area | 8 acres |
| Drainage Area | 1 sq mi |
| Max Discharge | 3,000 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | Alexander & Baldwin, Inc., Eric A. Knudsen Trust |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Unsatisfactory |
| Last Inspection | 03/06/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | HI00113 |
| Federal ID | HI00113 |
| More Info | State Dam Safety Program |