Thorstensen 3 Reservoir Report
Nearby: M.A. Cnot Ratedtis Fred Joens
Last Updated: December 13, 2025
Thorstensen 3, a privately-owned dam located in Dewey, South Dakota, was completed in 1969 and stands at a height of 25 feet.
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Summary
This earth dam on the TR-MOREAU river has a maximum storage capacity of 24 acre-feet and a normal storage of 12 acre-feet. With a low hazard potential and a condition assessment of "Not Rated", Thorstensen 3 plays a crucial role in water resource management in the region.
Managed by the South Dakota Department of Environment and Natural Resources (DENR), Thorstensen 3 is subject to state regulation, inspection, and enforcement to ensure its safety and functionality. The dam is designed to handle a maximum discharge of 1800 cubic feet per second and has not been modified in recent years. Despite its low hazard potential, the dam's emergency action plan status and risk management measures remain unspecified.
As water resource and climate enthusiasts continue to monitor and advocate for sustainable water infrastructure, Thorstensen 3 serves as a tangible example of the importance of proper dam maintenance and regulation in mitigating potential risks and ensuring the safety of surrounding communities and ecosystems. Its role in water storage and flood control on the TR-MOREAU river highlights the interconnectedness of water resource management and climate resilience in the region.
Year Completed |
1969 |
Dam Length |
270 |
Dam Height |
25 |
River Or Stream |
TR-MOREAU |
Primary Dam Type |
Earth |
Hydraulic Height |
25 |
Nid Storage |
24 |
Hazard Potential |
Low |
Nid Height |
25 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Moreau R Near Whitehorse Sd
|
35cfs |
Grand R At Little Eagle Sd
|
47cfs |
Oak Cr Near Wakpala Sd
|
10cfs |
Moreau R Near Faith Sd
|
14cfs |
Cedar Creek Nr Raleigh
|
20cfs |
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.
Thorstensen 3