Mcdonald Reservoir Report
Nearby: Kicking Horse Swartz Lake Dam
Last Updated: December 5, 2025
Mcdonald is a federal-owned irrigation dam located in Moiese, Montana, along the Post Creek.
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Summary
Built in 1920 by the Bureau of Indian Affairs, this Earth dam stands at 47 feet tall and stretches 1495 feet in length. With a capacity of 8225 acre-feet, Mcdonald serves the primary purpose of irrigation in the region. Despite being a crucial water resource, the dam has a high hazard potential and is classified as very high risk, emphasizing the need for careful monitoring and maintenance.
Owned, funded, designed, constructed, regulated, and inspected by the Bureau of Indian Affairs, Mcdonald is a significant water infrastructure project in the region. While it has not been assessed for condition recently, emergency action plans have been prepared and updated to ensure timely responses in case of any unforeseen events. With a high hazard potential, the dam's risk management measures are critical to safeguarding the surrounding communities and infrastructure from potential harm.
With a controlled spillway type and a history dating back to the early 20th century, Mcdonald plays a vital role in supporting agricultural activities in the area. Despite its age, the dam continues to provide essential irrigation water, highlighting the importance of ongoing monitoring and risk assessment to ensure its continued safe operation. For water resource and climate enthusiasts, Mcdonald presents a fascinating case study in the intersection of infrastructure, environmental stewardship, and community safety.
Year Completed |
1920 |
Dam Length |
1495 |
River Or Stream |
POST CREEK |
Primary Dam Type |
Earth |
Nid Storage |
8225 |
Structural Height |
47 |
Hazard Potential |
High |
Nid Height |
47 |
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.
Mcdonald