Upper Big Nemaha L-12 Reservoir Report
Last Updated: December 5, 2025
Upper Big Nemaha L-12 is a local government-owned earth dam located in Lancaster, Nebraska, designed by the USDA NRCS and completed in 1982.
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Summary
The dam stands at a height of 22 feet and has a storage capacity of 160 acre-feet, with a normal storage level of 34 acre-feet. Its primary purposes include flood risk reduction and other functions, serving the TR-N FK BIG NEMAHA RIVER. The dam has a low hazard potential and is in satisfactory condition as of the last inspection in September 2016.
Situated in the Omaha District, Upper Big Nemaha L-12 plays a crucial role in water resource management in the region, with a drainage area of 0.8 square miles and a maximum discharge capacity of 714 cubic feet per second. The dam's structural height reaches 25 feet, with a length of 535 feet and a surface area of 9 acres. It is regulated by the Nebraska Department of Natural Resources, with state permitting, inspection, and enforcement mechanisms in place to ensure its safe operation and maintenance.
For water resource and climate enthusiasts, Upper Big Nemaha L-12 represents a key infrastructure for flood control and water storage in the area. Its role in mitigating flood risks and managing water flow in the TR-N FK BIG NEMAHA RIVER watershed highlights the importance of such structures in ensuring water security and resilience to changing climate conditions. With its solid design and satisfactory condition, Upper Big Nemaha L-12 stands as a testament to effective water resource management and the collaborative efforts of local government and federal agencies in safeguarding the region's water resources.
Year Completed |
1982 |
Dam Length |
535 |
Dam Height |
22 |
River Or Stream |
TR-N FK BIG NEMAHA RIVER |
Primary Dam Type |
Earth |
Surface Area |
9 |
Hydraulic Height |
21 |
Drainage Area |
0.8 |
Nid Storage |
160 |
Structural Height |
25 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
25 |
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.
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