Dejong Bros 11 Reservoir Report
Nearby: Dejong Bros. 7 Dejong Bros 10
Last Updated: December 13, 2025
Dejong Bros 11 is a privately owned dam located in Lyman, South Dakota, along the TRIB-WHITE RIVER.
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Summary
This earth dam, completed in 1962, stands at a height of 25 feet and has a storage capacity of 25 acre-feet. With a maximum discharge of 672 cubic feet per second, the dam has a low hazard potential and is currently rated as "Not Rated" in terms of condition assessment.
Managed by the South Dakota Department of Environment and Natural Resources (DENR), Dejong Bros 11 is subject to state regulatory oversight, including permitting, inspection, and enforcement. Despite its age, the dam has not undergone any modifications in recent years, and its emergency action plan (EAP) status remains unprepared and unreviewed. While the risk assessment and management measures for the dam are currently unassigned, the structure is not owned or funded by any federal agencies.
For water resource and climate enthusiasts, Dejong Bros 11 presents an opportunity to explore a historic earth dam in South Dakota and learn about its hydrological characteristics and operational status. With its location in a riverine environment and under state jurisdiction, this dam serves as a case study in state-level dam management practices and the importance of regular inspection and maintenance to ensure public safety and environmental protection. Further research and monitoring of Dejong Bros 11 could provide valuable insights into sustainable water resource management and climate resilience strategies for similar structures in the region.
Year Completed |
1962 |
Dam Length |
182 |
Dam Height |
25 |
River Or Stream |
TRIB-WHITE RIVER |
Primary Dam Type |
Earth |
Hydraulic Height |
25 |
Nid Storage |
25 |
Hazard Potential |
Low |
Nid Height |
25 |
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 |
Platte Creek Near Platte
|
3cfs |
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 11