Ryno #2 Reservoir Report
Nearby: Derry Robert No.1 Van Collons No.1
Last Updated: December 12, 2025
Ryno #2 is a privately owned earth dam located in Mellette, South Dakota, along the TR White Thunder Creek offstream.
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Summary
Built in 1955, this dam stands at a height of 27 feet and has a storage capacity of 43 acre-feet, with a maximum discharge of 144 cubic feet per second. Despite being classified as having a low hazard potential, the dam's condition assessment has not been rated, indicating a need for further inspection and evaluation.
Managed by the South Dakota Department of Environment and Natural Resources (DENR), Ryno #2 is subject to state regulations, permitting, inspection, and enforcement. While there are no associated structures or modification records for this dam, its location within the St. Paul District of the US Army Corps of Engineers highlights its importance in water resource management. With Dusty Johnson representing the area as the congressional representative, the dam plays a crucial role in flood control and water supply for the region.
Although the dam's Emergency Action Plan (EAP) status and risk assessment details are not provided, the presence of a state-regulated dam in a rural area underscores the significance of water resource infrastructure in mitigating climate-related risks. As water resource and climate enthusiasts, understanding the regulatory framework and operational status of dams like Ryno #2 is essential for promoting sustainable water management practices and ensuring the safety and resilience of communities in the face of changing environmental conditions.
Year Completed |
1955 |
Dam Length |
222 |
Dam Height |
27 |
River Or Stream |
TR WHITE THUNDER CR OFFSTREAM |
Primary Dam Type |
Earth |
Hydraulic Height |
27 |
Nid Storage |
43 |
Hazard Potential |
Low |
Nid Height |
27 |
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.
Ryno #2