T.W. Lyman Reservoir Report
Nearby: Gustaue Aman Krumm Dam
Last Updated: December 13, 2025
T.W.
°F
°F
mph
Wind
%
Humidity
Summary
Lyman is a privately owned dam located in Corson, South Dakota, along the TR-OAK CREEK river. Built in 1940, this earth dam stands at a height of 19 feet and has a storage capacity of 175 acre-feet. With a maximum discharge of 2100 cubic feet per second, T.W. Lyman plays a crucial role in managing water resources in the area.
Managed by the South Dakota Department of Environment and Natural Resources (DENR), T.W. Lyman is regulated, inspected, and enforced by the state. The dam is classified as having a significant hazard potential, although its condition assessment is currently listed as "Not Rated." Despite lacking a detailed risk assessment or emergency action plan, T.W. Lyman remains a key infrastructure for water resource management in the region, providing essential flood control and water storage capabilities.
In the political landscape, T.W. Lyman falls within Dusty Johnson's (R) congressional district. While the dam has not undergone recent modifications or inspections, its presence underscores the importance of maintaining and monitoring critical water infrastructure to address climate-related challenges. Enthusiasts of water resources and climate resilience will find T.W. Lyman an intriguing case study in the intersection of infrastructure, regulation, and environmental stewardship.
Year Completed |
1940 |
Dam Length |
600 |
Dam Height |
19 |
River Or Stream |
TR-OAK CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
19 |
Nid Storage |
175 |
Hazard Potential |
Significant |
Nid Height |
19 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Oak Cr Near Wakpala Sd
|
10cfs |
Grand R At Little Eagle Sd
|
47cfs |
Cedar Creek Nr Raleigh
|
20cfs |
Cannonball River Nr Raleigh
|
40cfs |
Cannonball River At Breien
|
96cfs |
Beaver Creek Bl Linton
|
39cfs |
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.
T.W. Lyman