Dejong Bros 9 Reservoir Report
Nearby: Dejong Bros. 7 Dejong Bros 11
Last Updated: December 13, 2025
Dejong Bros 9 is a privately owned dam located in Lyman, South Dakota, along the TRIB-WHITE RIVER.
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Summary
Constructed in 1962, this earth-type dam stands at a height of 26 feet and has a length of 274 feet. With a storage capacity of 20 acre-feet, Dejong Bros 9 serves multiple purposes such as flood control, irrigation, and water supply for the surrounding area.
Managed by the South Dakota Department of Environment and Natural Resources (DENR), Dejong Bros 9 is regulated, permitted, inspected, and enforced by state authorities to ensure its safety and functionality. With a low hazard potential and a current condition assessment of "Not Rated," the dam is considered to be in satisfactory condition. Although its emergency action plan and risk assessment measures are not fully disclosed, Dejong Bros 9 remains a crucial piece of infrastructure for water resource management in the area.
As a vital structure in the St. Paul District, Dejong Bros 9 plays a significant role in water resource management in South Dakota. With its modest size and low hazard potential, this dam serves as a reliable asset for both water supply and flood control in the region. As climate change continues to impact water resources, the proper maintenance and monitoring of dams like Dejong Bros 9 are essential to ensure the safety and sustainability of water systems in the face of evolving environmental challenges.
Year Completed |
1962 |
Dam Length |
274 |
Dam Height |
26 |
River Or Stream |
TRIB-WHITE RIVER |
Primary Dam Type |
Earth |
Hydraulic Height |
26 |
Nid Storage |
20 |
Hazard Potential |
Low |
Nid Height |
26 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
White R Near Oacoma Sd
|
105cfs |
White River Near White River
|
42cfs |
Keya Paha R Near Keyapaha Sd
|
33cfs |
Little White R Below White River Sd
|
141cfs |
Bad R Near Fort Pierre Sd
|
7cfs |
Keya Paha R At Wewela Sd
|
54cfs |
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.
Dejong Bros 9