Upper Big Nemaha 2-A Reservoir Report
Last Updated: December 6, 2025
Upper Big Nemaha 2-A, located in Johnson County, Nebraska, is a local government-owned dam designed by the USDA NRCS for flood risk reduction along the TR-N FK BIG NEMAHA RIVER.
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Summary
Completed in 1972, this earth dam stands at 35 feet in height, with a hydraulic height of 33 feet and a structural height of 37 feet. With a storage capacity of 749 acre-feet, it serves the primary purpose of flood risk reduction and has a drainage area of 2.3 square miles.
Despite its low hazard potential, Upper Big Nemaha 2-A has been assessed as being in poor condition as of June 2016. The dam has a normal storage capacity of 120 acre-feet and a maximum discharge of 1296 cubic feet per second. The dam spans 1165 feet in length and covers a surface area of 21 acres. While the dam is under state regulation and inspection by the NE DNR, there are no federal agency involvements in its ownership, funding, design, construction, or operation.
Water resource and climate enthusiasts interested in the infrastructure of Upper Big Nemaha 2-A can track its condition and maintenance through regular inspections, with the next one scheduled in 2021. Despite its poor condition assessment, the dam continues to serve its purpose of mitigating flood risks in the area. As a vital component of the local flood management system, Upper Big Nemaha 2-A plays a crucial role in safeguarding the surrounding community from potential water-related emergencies.
Year Completed |
1972 |
Dam Length |
1165 |
Dam Height |
35 |
River Or Stream |
TR-N FK BIG NEMAHA RIVER |
Primary Dam Type |
Earth |
Surface Area |
21 |
Hydraulic Height |
33 |
Drainage Area |
2.3 |
Nid Storage |
749 |
Structural Height |
37 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
37 |
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 2-A