Ackley Lake Dam
Ackley Lake Dam is an earth dam located in Judith Basin County, Montana, built in 1938. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Ackley Lake Dam
The primary purpose of Ackley 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 State Water Projects (state). It impounds the Tr-hauck Coulee.
The dam stands 55 feet tall and stretches 3,514 feet across, creates a reservoir covering 260 acres, has a maximum storage capacity of 8,315 acre-feet, and collects water from a drainage area of 2 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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 10/03/2024.
At 55 feet, this dam is taller than 94% 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 Montana 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 | Montana |
| County | Judith Basin |
| Nearest City | None |
| River/Stream | Tr-hauck Coulee |
| Coordinates | 46.95857, -109.93290 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 55 ft |
| Dam Height | 55 ft |
| Dam Length | 3,514 ft |
| Year Completed | 1938 (88 years old) |
Storage & Hydraulics
| NID Storage | 8,315 acre-ft |
| Max Storage | 8,315 acre-ft |
| Normal Storage | 5,970 acre-ft |
| Surface Area | 260 acres |
| Drainage Area | 2 sq mi |
| Max Discharge | 1,410 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | STATE WATER PROJECTS |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 10/03/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MT00010 |
| Federal ID | MT00010 |
| More Info | State Dam Safety Program |