Upper Big Nemaha 13-A Reservoir Report

Last Updated: December 5, 2025

Upper Big Nemaha 13-A is a local government-owned earth dam located in Lancaster, Nebraska, along the TR-MID BR Big Nemaha River.


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Summary

Built in 1970 by the USDA NRCS, this dam stands at a height of 23 feet and serves primarily for flood risk reduction purposes. With a normal storage capacity of 41 acre-feet and a maximum storage of 398 acre-feet, the dam covers a surface area of 11 acres and has a drainage area of 0.7 square miles.

Managed by the Nebraska Department of Natural Resources, Upper Big Nemaha 13-A has a low hazard potential and is in satisfactory condition as of the last inspection in June 2016. The dam has a structural height of 27 feet and a hydraulic height of 22 feet, with a maximum discharge capacity of 1270 cubic feet per second. While no spillway type is specified, the dam does not have any associated locks or gates. Despite being non-USACE managed, this earth dam plays a crucial role in protecting the local community from potential flooding events in the area.

Overall, Upper Big Nemaha 13-A is an essential infrastructure for flood risk reduction in the region, with its satisfactory condition and low hazard potential providing reassurance to the local community. With the Nebraska Department of Natural Resources overseeing its regulation, inspection, and enforcement, this dam serves as a key component in managing water resources and climate-related risks in the area. As climate change continues to impact water systems, the importance of well-maintained structures like Upper Big Nemaha 13-A becomes increasingly evident in ensuring the safety and resilience of the surrounding environment.

Year Completed

1970

Dam Length

825

Dam Height

23

River Or Stream

TR-MID BR BIG NEMAHA RIVER

Primary Dam Type

Earth

Surface Area

11

Hydraulic Height

22

Drainage Area

0.7

Nid Storage

398

Structural Height

27

Hazard Potential

Low

Foundations

Soil

Nid Height

27
       
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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.