Nelson Dam No. 2 Reservoir Report
Nearby: Sandoz Dam Ebersoll Dam
Last Updated: December 6, 2025
Nelson Dam No.
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Summary
2, located in South Dakota along the WEST FORK HAY CANYON, is a Federal-owned structure designed by DUCKS UNLIMITED. Built in 1999, this Earth type dam stands at a height of 23 feet and spans 950 feet in length, with a storage capacity of 123 acre-feet. With a low hazard potential and a moderate risk assessment rating, this dam plays a crucial role in water resource management in the area.
Despite not being regulated or inspected by the state, Nelson Dam No. 2 serves as a vital infrastructure for flood control and water storage, with a maximum discharge capacity of 620 cubic feet per second. The dam's uncontrolled spillway, with a width of 60 feet, helps manage excess water flow during heavy rainfall events. While its condition is currently not rated, the dam's risk management measures are in place to ensure its continued functionality.
Situated within the Fall River county of South Dakota, Nelson Dam No. 2 presents an interesting case study for water resource and climate enthusiasts. Its strategic location, design features, and operational history contribute to the broader conversation on dam infrastructure and its role in maintaining water security in the region.
Year Completed |
1999 |
Dam Length |
950 |
Dam Height |
23 |
River Or Stream |
WEST FORK HAY CANYON |
Primary Dam Type |
Earth |
Hydraulic Height |
23 |
Drainage Area |
2 |
Nid Storage |
123 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
23 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
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.
Nelson Dam No. 2