Upper Big Nemaha J-42 Reservoir Report
Last Updated: December 6, 2025
Upper Big Nemaha J-42 is a vital water resource structure located in Johnson, Nebraska, along the TR-N FK BIG NEMAHA RIVER.
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Summary
This earth dam, designed by USDA NRCS and completed in 1972, serves multiple purposes including flood risk reduction. With a height of 29 feet and a length of 728 feet, the dam has a storage capacity of 189 acre-feet and covers a drainage area of 0.7 square miles.
Managed by the local government and regulated by the NE DNR, Upper Big Nemaha J-42 has a low hazard potential and is currently in satisfactory condition. The dam's inspection frequency is every 5 years, with the last assessment conducted in June 2016. Located in a picturesque setting, this structure plays a crucial role in water resource management in the region, ensuring the safety and well-being of the surrounding community.
As climate change continues to impact water resources, structures like Upper Big Nemaha J-42 are essential for mitigating flood risks and ensuring water security. With its strategic location and effective design, this dam stands as a testament to the importance of sustainable water management practices in the face of a changing climate.
Year Completed |
1972 |
Dam Length |
728 |
Dam Height |
24 |
River Or Stream |
TR-N FK BIG NEMAHA RIVER |
Primary Dam Type |
Earth |
Surface Area |
8 |
Hydraulic Height |
22 |
Drainage Area |
0.7 |
Nid Storage |
189 |
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-42