Upper Big Nemaha 20-A Reservoir Report
Last Updated: December 6, 2025
Upper Big Nemaha 20-A is a locally owned earth dam in Johnson, Nebraska, designed by the USDA NRCS for flood risk reduction along the TR-N FK BIG NEMAHA RIVER.
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Summary
Completed in 1980, this dam stands at 40 feet tall with a hydraulic height of 38.14 feet, serving a primary purpose of flood risk reduction. With a storage capacity of 534 acre-feet and a drainage area of 1.7 square miles, it plays a crucial role in managing water levels and protecting the surrounding area from potential flooding events.
Managed by the NE DNR, Upper Big Nemaha 20-A has a low hazard potential and is deemed to be in satisfactory condition based on the last inspection in 2016. The dam has a normal storage capacity of 136 acre-feet and a surface area of 17 acres, making it an essential infrastructure for water resource management in the region. Despite being non-USACE owned, this local government-owned dam plays a significant role in mitigating flood risks and ensuring the safety of the community.
Located in Sterling, Nebraska, Upper Big Nemaha 20-A is a vital component of the local water resource infrastructure, with a history of effective flood risk reduction since its completion in 1980. With state jurisdiction, inspection, and enforcement in place, the dam continues to serve its purpose efficiently, safeguarding the area from potential inundation events. As a key player in the Nebraska water resource landscape, this earth dam stands as a testament to the importance of proactive flood risk management in the face of changing climate patterns and water-related challenges.
Year Completed |
1980 |
Dam Length |
889 |
Dam Height |
40 |
River Or Stream |
TR-N FK BIG NEMAHA RIVER |
Primary Dam Type |
Earth |
Surface Area |
17 |
Hydraulic Height |
38.14 |
Drainage Area |
1.7 |
Nid Storage |
534 |
Structural Height |
50 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
50 |
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.
Upper Big Nemaha 20-A