Upper Big Nemaha 15-B Reservoir Report

Last Updated: December 5, 2025

Located in Lancaster, Nebraska, Upper Big Nemaha 15-B is a local government-owned earth dam designed by USDA NRCS and completed in 1970 for the primary purpose of flood risk reduction.


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Summary

The dam stands at a height of 22 feet with a structural height of 26 feet, spanning 713 feet in length. It has a storage capacity of 235 acre-feet and a normal storage of 29 acre-feet, serving a drainage area of 0.5 square miles along the TR-MID BR Big Nemaha River.

With a low hazard potential and a satisfactory condition assessment as of October 2016, Upper Big Nemaha 15-B is regulated by the Nebraska Department of Natural Resources, with state permitting, inspection, and enforcement in place. The dam's location in Firth, Nebraska, underscores its importance in mitigating flood risks and protecting the surrounding area. Water resource and climate enthusiasts will appreciate the role of this dam in managing water levels and ensuring the safety of the community.

Year Completed

1970

Dam Length

713

Dam Height

22

River Or Stream

TR-MID BR BIG NEMAHA RIVER

Primary Dam Type

Earth

Surface Area

9

Hydraulic Height

22

Drainage Area

0.5

Nid Storage

235

Structural Height

26

Hazard Potential

Low

Foundations

Soil

Nid Height

26
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.