Mann Dam Reservoir Report
Nearby: Dickinson Queen City Dam
Last Updated: December 7, 2025
Mann Dam, located in Dickinson, North Dakota, was completed in 1930 and serves primarily for irrigation purposes along the Heart River.
°F
°F
mph
Wind
%
Humidity
Summary
This buttress dam stands at a height of 12 feet and has a length of 125 feet, with a storage capacity of 53 acre-feet. The dam is regulated by the North Dakota State Water Commission and undergoes regular inspections and enforcement measures to ensure its safety and functionality.
Despite being classified as low hazard potential, Mann Dam has a moderate risk assessment rating of 3 due to its age and structural modifications made in 1973. The dam features an uncontrolled spillway with a width of 100 feet and a slide gate outlet. The surrounding area has a drainage area of 430 acres, with a surface area of 6 acres. The dam is not currently rated for its condition, but it meets state permitting and inspection requirements.
For water resource and climate enthusiasts, Mann Dam offers a unique glimpse into early 20th-century engineering practices and the vital role of dams in supporting agricultural irrigation in the region. With its historical significance and ongoing regulatory oversight, Mann Dam serves as a reminder of the importance of maintaining and monitoring critical water infrastructure for the benefit of local communities and ecosystems along the Heart River.
Years Modified |
1973 - Structural |
Year Completed |
1930 |
Dam Length |
125 |
Dam Height |
12 |
River Or Stream |
HEART RIVER |
Primary Dam Type |
Buttress |
Surface Area |
6 |
Drainage Area |
430 |
Nid Storage |
53 |
Outlet Gates |
Slide (sluice gate) - 1 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
12 |
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.
Mann Dam