Johnson Reservoir Report
Nearby: Milton Trask Old Town Dam
Last Updated: December 6, 2025
Johnson is a privately owned dam located in Pennington, South Dakota, along the TR-BAD River.
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Summary
Built in 1956, this earth dam stands at a height of 19 feet and has a length of 1400 feet, providing a storage capacity of 517 acre-feet. The dam is under the jurisdiction of the South Dakota Department of Environment and Natural Resources (DENR), and is regulated, permitted, inspected, and enforced by the state.
Managed by the Natural Resources Conservation Service, Johnson has a low hazard potential and is currently rated as "Not Rated" in terms of condition assessment. While the dam has not been recently inspected or assessed for emergency preparedness, it meets state guidelines for operation and maintenance. With a maximum discharge of 1250 cubic feet per second, Johnson plays a crucial role in water resource management and climate resilience in the region.
As a vital structure in the St. Paul District, Johnson serves as a key component of the local water infrastructure, contributing to flood control, water supply, and environmental conservation efforts. Climate enthusiasts and water resource experts alike can appreciate the significance of Johnson in preserving and managing water resources in Pennington County, South Dakota, under the careful oversight of state regulatory agencies.
Year Completed |
1956 |
Dam Length |
1400 |
Dam Height |
19 |
River Or Stream |
TR-BAD RIVER |
Primary Dam Type |
Earth |
Hydraulic Height |
19 |
Nid Storage |
517 |
Hazard Potential |
Low |
Nid Height |
19 |
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.
Johnson