Oscar Diess Reservoir Report
Nearby: Schindler Dam Reliance Dam
Last Updated: December 13, 2025
Oscar Diess, located in Lyman, South Dakota, is a privately owned dam regulated by the Department of Environment and Natural Resources.
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Summary
Built in 1953, this earth-type dam stands at a height of 22 feet and has a storage capacity of 63 acre-feet. With a low hazard potential and a current condition assessment of "Not Rated," Oscar Diess plays a crucial role in managing water resources in the area and ensuring the safety of surrounding communities.
Managed by the Natural Resources Conservation Service, Oscar Diess serves the primary purpose of regulating water flow in the Whiteriver Offstream, with a maximum discharge capacity of 438 cubic feet per second. Despite its age, the dam remains operational and compliant with state regulations for inspection, permitting, and enforcement. While the dam has not been rated for condition assessment, its low hazard potential indicates a relatively low risk of failure.
As a key component of the St. Paul District's water resource infrastructure, Oscar Diess contributes to flood control, irrigation, and water supply management in the region. While the dam has not been assigned an Emergency Action Plan (EAP) or undergone recent risk assessments, its presence highlights the importance of maintaining and monitoring water infrastructure to ensure the continued resilience of communities and ecosystems in South Dakota.
Year Completed |
1953 |
Dam Length |
520 |
Dam Height |
22 |
River Or Stream |
WHITERIVER OFFSTREAM |
Primary Dam Type |
Earth |
Hydraulic Height |
22 |
Nid Storage |
63 |
Hazard Potential |
Low |
Nid Height |
22 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
White R Near Oacoma Sd
|
105cfs |
Bad R Near Fort Pierre Sd
|
7cfs |
Platte Creek Near Platte
|
3cfs |
White River Near White River
|
42cfs |
Keya Paha R Near Keyapaha Sd
|
33cfs |
Little White R Below White River Sd
|
141cfs |
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.
Oscar Diess