Rock Cowan No. 4 Reservoir Report
Nearby: Rock Cowan No.2 Rock Cowan No. 1
Last Updated: December 7, 2025
Rock Cowan No.
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Summary
4 is a privately owned dam located in Dewey, South Dakota, along the TR MOREAU river. Built in 1964, this Earth-type dam stands at a height of 25 feet and has a length of 400 feet, with a storage capacity of 50 acre-feet. Despite its age, the dam is in good condition and has a low hazard potential, making it a reliable structure for water resource management in the area.
Managed by the South Dakota Department of Environment and Natural Resources (DENR), Rock Cowan No. 4 is subject to state regulations, inspections, and enforcement to ensure its safety and compliance with standards. With a maximum discharge capacity of 2440 cubic feet per second, the dam plays a crucial role in flood control and water storage, benefiting the local community and ecosystem. The dam's proximity to St. Paul District of the US Army Corps of Engineers further highlights its significance in water resource management in the region.
While not currently rated for its condition, Rock Cowan No. 4 remains a key infrastructure for water management in Dewey, South Dakota. With its low hazard potential and state oversight, the dam serves as a reliable structure for ensuring water security and mitigating flood risks in the area. As climate change continues to impact water resources, the importance of well-maintained dams like Rock Cowan No. 4 becomes increasingly vital for adapting to changing conditions and safeguarding the environment.
Year Completed |
1964 |
Dam Length |
400 |
Dam Height |
25 |
River Or Stream |
TR MOREAU |
Primary Dam Type |
Earth |
Hydraulic Height |
25 |
Nid Storage |
50 |
Hazard Potential |
Low |
Nid Height |
25 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Moreau R Near Whitehorse Sd
|
35cfs |
Moreau R Near Faith Sd
|
14cfs |
Cheyenne R Near Plainview Sd
|
0cfs |
Grand R At Little Eagle Sd
|
47cfs |
Oak Cr Near Wakpala Sd
|
10cfs |
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.
Rock Cowan No. 4