John Holloway Reservoir Report
Nearby: Glen Bringman Gail Vrooman
Last Updated: December 8, 2025
John Holloway is a privately owned earth dam located in Dewey, South Dakota, along the TR MOREAU river.
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Summary
This dam, completed in 1945, stands at a height of 18 feet and has a storage capacity of 56 acre-feet, with a maximum discharge of 2000 cubic feet per second. Despite being classified as having a low hazard potential, its condition is currently not rated.
Managed by the South Dakota Department of Environment and Natural Resources (DENR), John Holloway is subject to state regulations, permitting, inspection, and enforcement. The dam's primary purpose and associated structures are not specified, but it serves the local community by providing flood control and water storage along the river. The dam's emergency action plan (EAP) status, risk assessment, and management measures are also unspecified at this time.
Located within the St. Paul District of the US Army Corps of Engineers, John Holloway has not been modified in recent years and lacks detailed information on its outlet gates, inspection frequency, and maintenance history. While it currently meets guidelines for emergency preparedness and has not been rated as a significant risk, there is a need for further evaluation and documentation to ensure the safety and efficiency of this water resource in the face of potential climate challenges.
Year Completed |
1945 |
Dam Length |
500 |
Dam Height |
18 |
River Or Stream |
TR MOREAU |
Primary Dam Type |
Earth |
Hydraulic Height |
18 |
Nid Storage |
56 |
Hazard Potential |
Low |
Nid Height |
18 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Moreau R Near Whitehorse Sd
|
35cfs |
Grand R At Little Eagle Sd
|
47cfs |
Cheyenne R Near Plainview Sd
|
0cfs |
Moreau R Near Faith Sd
|
14cfs |
Oak Cr Near Wakpala Sd
|
10cfs |
Bad R Near Fort Pierre Sd
|
7cfs |
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.
John Holloway