Jensen Number 1 Reservoir Report
Nearby: Jensen Number 8 Atkinson No.1
Last Updated: December 8, 2025
Jensen Number 1 is a privately owned earth dam located in Mellette, South Dakota, along the TR Cottonwood Offstream.
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Summary
Built in 1962, the dam stands at a height of 34 feet with a hydraulic height of 30 feet and a length of 450 feet. The dam has a maximum storage capacity of 30 acre-feet and a normal storage level of 23 acre-feet, serving as a crucial water resource for the surrounding area.
Managed by the South Dakota Department of Environment and Natural Resources, Jensen Number 1 is regulated and inspected regularly to ensure its safety and functionality. Despite being rated as low hazard potential and in not-rated condition, the dam plays a significant role in flood control and water supply management in the region. With a maximum discharge capacity of 2500 cubic feet per second, the dam is equipped to handle varying water levels efficiently.
Owned by a private entity and overseen by the Natural Resources Conservation Service, Jensen Number 1 serves as a key infrastructure for water resource management in South Dakota. With its strategic location and robust design, the dam continues to play a vital role in safeguarding the local environment and providing essential water resources for the community.
Year Completed |
1962 |
Dam Length |
450 |
Dam Height |
34 |
River Or Stream |
TR COTTONWOOD OFFSTREAM |
Primary Dam Type |
Earth |
Hydraulic Height |
30 |
Nid Storage |
30 |
Hazard Potential |
Low |
Nid Height |
34 |
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.
Jensen Number 1