Upper Big Nemaha J-40 Reservoir Report
Last Updated: December 6, 2025
Located in Johnson, Nebraska, the Upper Big Nemaha J-40 dam stands as a vital structure designed by the USDA NRCS to mitigate flood risks and serve other purposes.
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Summary
Completed in 1967, this earth-type dam stands at a height of 25 feet with a length of 370 feet, offering a storage capacity of 50 acre-feet and serving a drainage area of 0.24 square miles. The dam's low hazard potential and satisfactory condition assessment make it a reliable asset for the local government in Sterling.
Managed by the NE DNR, Upper Big Nemaha J-40 undergoes regular inspections every five years to ensure its structural integrity and functionality. With a maximum discharge capacity of 596 cubic feet per second, the dam plays a crucial role in managing water flow and reducing flood risks in the area. The dam's location on TR-Hooker Creek highlights its importance in safeguarding the surrounding community from potential water-related disasters.
With its historical significance dating back to over five decades, Upper Big Nemaha J-40 continues to play a crucial role in water resource management in Nebraska. As a key component of flood risk reduction efforts, this dam, designed and maintained by the Natural Resources Conservation Service, stands as a testament to effective water infrastructure that serves both practical and environmental purposes in the region.
Year Completed |
1967 |
Dam Length |
370 |
Dam Height |
25 |
River Or Stream |
TR-HOOKER CREEK |
Primary Dam Type |
Earth |
Surface Area |
3 |
Hydraulic Height |
25 |
Drainage Area |
0.24 |
Nid Storage |
50 |
Structural Height |
29 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
29 |
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 J-40