Upper Big Nemaha 21-A Reservoir Report

Last Updated: December 5, 2025

Upper Big Nemaha 21-A is a vital earth dam located in Otoe, Nebraska, designed by USDA NRCS and completed in 1983 with a primary purpose of flood risk reduction.


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Summary

With a height of 33 feet and a length of 908 feet, the dam serves to protect the surrounding area from potential flooding events, storing up to 427 acre-feet of water during times of high discharge. Managed by the Nebraska Department of Natural Resources, the dam is inspected every 5 years and has been assessed as having a low hazard potential and satisfactory condition.

Situated along the TR-MID BR Big Nemaha River, Upper Big Nemaha 21-A plays a crucial role in mitigating flood risks in the region, covering a surface area of 24 acres and draining a 1.8 square mile watershed. Owned and regulated by local government authorities, the dam's operations are overseen by the Nebraska DNR to ensure its effectiveness in flood control. While the dam has not been modified since its completion, it continues to stand as a reliable infrastructure for water resource management in the area, with a comprehensive emergency action plan in place to address any potential risks or incidents.

As a key component of the flood risk reduction system in Otoe, Nebraska, Upper Big Nemaha 21-A stands as a testament to the collaborative efforts of local government agencies and the USDA NRCS in safeguarding the community from potential water-related disasters. With its stone core and soil foundation, the dam serves as a critical structure for managing water flow and protecting the surrounding environment. Through regular inspections and maintenance, the dam continues to uphold its role in ensuring the safety and resilience of the area against the impacts of extreme weather events and changing climate patterns.

Year Completed

1983

Dam Length

908

Dam Height

33

River Or Stream

TR-MID BR BIG NEMAHA RIVER

Primary Dam Type

Earth

Surface Area

24

Hydraulic Height

29

Drainage Area

1.8

Nid Storage

427

Structural Height

33

Hazard Potential

Low

Foundations

Soil

Nid Height

33
       
Seasonal Comparison

Weather Forecast

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Nearby Streamflow Levels

Upper Big Nemaha 21-ASALT CREEK AT ROCA Preview Salt Creek At Roca
4.93cfs
5cfs
Upper Big Nemaha 21-ASALT CREEK AT PIONEERS BLVD AT LINCOLN Preview Salt Creek At Pioneers Blvd At Lincoln
10.5cfs
11cfs
Upper Big Nemaha 21-ASTEVENS CREEK NR. LINCOLN Preview Stevens Creek Nr. Lincoln
2.69cfs
3cfs
Upper Big Nemaha 21-AHAINES BRANCH AT SW 56th ST. AT LINCOLN Preview Haines Branch At Sw 56th St. At Lincoln
1.33cfs
1cfs
Upper Big Nemaha 21-ASALT CREEK AT LINCOLN Preview Salt Creek At Lincoln
76.6cfs
77cfs
Upper Big Nemaha 21-ATURKEY CREEK NEAR DE WITT Preview Turkey Creek Near De Witt
10.1cfs
10cfs

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.
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