Earl Hanrahan Reservoir Report
Nearby: Sd Noname 201 Sd Noname 280
Last Updated: December 5, 2025
Earl Hanrahan is a privately owned dam located in Haakon, South Dakota, along the TR Cheyenne River.
°F
°F
mph
Wind
%
Humidity
Summary
This Earth-type dam was completed in 1949 and stands at a height of 12 feet with a length of 200 feet, providing a maximum storage capacity of 67 acre-feet. While the dam has a low hazard potential, its condition is currently not rated, and the last inspection date is unknown.
Managed by the Natural Resources Conservation Service, Earl Hanrahan plays a crucial role in water resource management in the area. With state regulation, permitting, inspection, and enforcement in place, the dam ensures the safety and integrity of the surrounding environment. Despite its age, Earl Hanrahan continues to serve its primary purpose effectively, contributing to the overall water conservation efforts in South Dakota.
For water resource and climate enthusiasts, Earl Hanrahan serves as a significant landmark in the St. Paul District, providing essential water storage and flood control along the TR Cheyenne River. As climate change impacts water resources, understanding the role of structures like Earl Hanrahan becomes increasingly important in managing and mitigating potential risks. With ongoing regulatory oversight and management measures in place, Earl Hanrahan stands as a testament to the importance of sustainable water resource management in the face of changing environmental conditions.
Year Completed |
1949 |
Dam Length |
200 |
Dam Height |
12 |
River Or Stream |
TR CHEYENNE RIVER |
Primary Dam Type |
Earth |
Hydraulic Height |
12 |
Nid Storage |
67 |
Hazard Potential |
Low |
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.
Earl Hanrahan