Ackley Lake Dam Reservoir Report
Last Updated: December 24, 2025
Ackley Lake Dam, located in Judith Basin, Montana, is a state-regulated earth dam built in 1938 primarily for irrigation purposes.
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Summary
With a height of 55 feet and a storage capacity of 8,315 acre-feet, the dam sits on the TR-Hauck Coulee and has a drainage area of 2.6 square miles. The dam's spillway type is uncontrolled, with a width of 17 feet, and it has a maximum discharge capacity of 1,410 cubic feet per second.
The dam, managed by the Department of Natural Resources and Conservation (DNRC), has a high hazard potential but is currently in a satisfactory condition, as assessed in December 2020. The last inspection in October 2021 showed that the dam meets safety standards, with an inspection frequency of every 5 years. Although the dam's risk assessment is moderate, with a rating of 3, there are no specific risk management measures or inundation maps prepared at this time.
For water resource and climate enthusiasts, Ackley Lake Dam represents a significant infrastructure for irrigation in the area, providing vital water storage for agricultural activities. The dam's historical significance, solid structural integrity, and ongoing regulatory oversight by the state make it an essential component of water management in the region. The dam's location and specifications make it an interesting subject for further study and monitoring in the context of changing climate conditions and water resource management strategies.
Year Completed |
1938 |
Dam Length |
3514 |
Dam Height |
55 |
River Or Stream |
TR-HAUCK COULEE |
Primary Dam Type |
Earth |
Surface Area |
260 |
Hydraulic Height |
51 |
Drainage Area |
2.6 |
Nid Storage |
8315 |
Hazard Potential |
High |
Foundations |
Rock |
Nid Height |
55 |
Seasonal Comparison
Weather Forecast
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.
Ackley Lake Dam