Thompson Dam Reservoir Report
Nearby: Reliance Dam Larsen Dam
Last Updated: December 13, 2025
Thompson Dam, located in Lyman, South Dakota, is a privately owned earth dam that was completed in 2010 by the USDA NRCS.
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Summary
This dam, situated on the TR BAD River, has a height of 23 feet and a storage capacity of 74 acre-feet. With a low hazard potential and a moderate risk assessment rating, Thompson Dam plays a crucial role in water resource management in the region.
Managed by the South Dakota Department of Environment and Natural Resources (DENR), Thompson Dam is regulated, permitted, inspected, and enforced by state authorities to ensure its safety and effectiveness. The dam features an uncontrolled spillway with a width of 40 feet and a maximum discharge capacity of 1080 cubic feet per second. While the dam's condition is currently rated as "Not Rated," regular inspections and maintenance are conducted to uphold its structural integrity.
Thompson Dam serves as a vital infrastructure for water storage and flood control in the area, contributing to the overall water resource management efforts. With its strategic location and design features, this dam stands as a testament to the collaboration between private ownership and state regulatory agencies in safeguarding water resources and mitigating climate-related risks in South Dakota.
Year Completed |
2010 |
Dam Length |
292 |
Dam Height |
23 |
River Or Stream |
TR BAD RIVER |
Primary Dam Type |
Earth |
Hydraulic Height |
23 |
Drainage Area |
1 |
Nid Storage |
74 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
23 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
White R Near Oacoma Sd
|
105cfs |
Platte Creek Near Platte
|
3cfs |
Bad R Near Fort Pierre Sd
|
7cfs |
White River Near White River
|
42cfs |
Keya Paha R Near Keyapaha Sd
|
33cfs |
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.
Thompson Dam