Mcdonald
Mcdonald is an earth dam located in Lake County, Montana, built in 1920. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Mcdonald
The primary purpose of Mcdonald is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Bia (federal). It impounds the Post Creek near Moiese.
The dam stands 47 feet tall and stretches 1,495 feet across, creates a reservoir covering 188 acres, has a maximum storage capacity of 8,645 acre-feet, and collects water from a drainage area of 21 square miles. Completed in 1920, 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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam.
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 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 | Lake |
| Nearest City | Moiese |
| River/Stream | Post Creek |
| Coordinates | 47.42380, -113.99260 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 47 ft |
| Dam Height | 47 ft |
| Dam Length | 1,495 ft |
| Year Completed | 1920 (106 years old) |
Storage & Hydraulics
| NID Storage | 8,645 acre-ft |
| Max Storage | 8,645 acre-ft |
| Normal Storage | 8,225 acre-ft |
| Surface Area | 188 acres |
| Drainage Area | 21 sq mi |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | BIA |
| Owner Type | Federal |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MT00590 |
| Federal ID | MT00590 |
| More Info | State Dam Safety Program |