Hewitt Dam Reservoir Report
Nearby: Nelson Dike A Nelson Dike B
Last Updated: December 6, 2025
Hewitt Dam, located in Phillips County, Montana, is a federal-owned structure primarily managed by the Department of Interior Fish and Wildlife Service.
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Summary
Built in 1938, this Earth-type dam serves as a Fish and Wildlife Pond with a capacity of 3,250 acre-feet of water from the Hewitt Lake Coulee. The dam stands at a height of 10 feet and has a hydraulic height of 7 feet, with a length of 1,180 feet and a surface area of 459 acres.
Despite its low hazard potential, the dam's condition assessment in 2020 was rated as poor, indicating a need for maintenance and potential upgrades. The structure has a moderate risk level, with a history of modifications and inspections by the Fish and Wildlife Service. With a maximum discharge capacity of 6,240 cubic feet per second, the dam plays a crucial role in managing water resources for the surrounding area while also providing habitat for fish and wildlife. As a key component of the local ecosystem, Hewitt Dam serves as a focal point for water resource and climate enthusiasts interested in conservation efforts in Montana.
Year Completed |
1938 |
Dam Length |
1180 |
Dam Height |
10 |
River Or Stream |
HEWITT LAKE COULEE |
Primary Dam Type |
Earth |
Surface Area |
459 |
Hydraulic Height |
7 |
Drainage Area |
17.4 |
Nid Storage |
3250 |
Structural Height |
10 |
Hazard Potential |
Low |
Nid Height |
10 |
Seasonal Comparison
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Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.
Hazard Potential Classification
HighDams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.
Hewitt Dam