Wilmarth Reservoir Report
Nearby: Fraser Estabrook Dam
Last Updated: December 12, 2025
Wilmarth is a state-owned dam located in South Dakota, specifically in Aurora County.
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Summary
Built in 1937 by the Works Progress Administration (WPA), this earth dam stands at a height of 31 feet with a length of 940 feet, creating a reservoir with a storage capacity of 2510 acre-feet. The dam is regulated by the South Dakota Department of Agriculture and Natural Resources (DANR) and is inspected regularly to ensure its structural integrity and safety.
Situated on the W Firesteel Creek, Wilmarth serves primarily for irrigation purposes within its 56 square mile drainage area. With a maximum discharge capacity of 5091 cubic feet per second, the dam's spillway is uncontrolled and measures 50 feet in width. Despite its low hazard potential, the dam is considered to have a moderate risk level, which emphasizes the importance of ongoing risk management and monitoring to prevent any potential emergencies or failures. The dam has not been rated for its current condition but is subject to routine inspections every three years.
In the event of an emergency, Wilmarth does not have an Emergency Action Plan (EAP) prepared, and its hazard potential is classified as low. However, given its age and moderate risk status, it is crucial for authorities to address any potential vulnerabilities and ensure that appropriate risk management measures are in place. With its historical significance and vital role in water resource management, Wilmarth represents a key infrastructure for the region, highlighting the importance of proactive maintenance and safety protocols to safeguard against any unforeseen events that may impact both the dam and the surrounding community.
Year Completed |
1937 |
Dam Length |
940 |
Dam Height |
31 |
River Or Stream |
W FIRESTEEL CREEK |
Primary Dam Type |
Earth |
Hydraulic Height |
31 |
Drainage Area |
56 |
Nid Storage |
2510 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
31 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Firesteel Cr Near Mount Vernon Sd
|
0cfs |
James R Near Forestburg Sd
|
560cfs |
James R Near Mitchell Sd
|
659cfs |
James R At Huron Sd
|
548cfs |
Platte Creek Near Platte
|
3cfs |
White R Near Oacoma Sd
|
105cfs |
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.
Wilmarth