Upper Big Nemaha G-18a Reservoir Report
Last Updated: December 6, 2025
Upper Big Nemaha G-18a is a local government-owned earth dam located in Gage County, Nebraska.
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Summary
Built in 1974 by the USDA NRCS, this dam serves multiple purposes including flood risk reduction and other water resource management activities. With a height of 24 feet and a length of 734 feet, it provides a storage capacity of 254 acre-feet and can handle a maximum discharge of 590 cubic feet per second.
Managed by the Nebraska Department of Natural Resources, Upper Big Nemaha G-18a has a low hazard potential and is in satisfactory condition as of the last inspection in May 2020. The dam is state-regulated and has state permitting, inspection, and enforcement in place to ensure its safety and functionality. While it does not have a spillway, the dam's primary purpose is to mitigate flood risks in the area and maintain water resources for the surrounding community.
Located in the watershed of Jakes Creek, Upper Big Nemaha G-18a plays a crucial role in water resource management in the region. With its stone core and soil foundation, this dam is a key component of the local water infrastructure. Climate and water resource enthusiasts will appreciate the efforts put into its design, construction, and ongoing maintenance to safeguard the community and its water supply.
Year Completed |
1974 |
Dam Length |
734 |
Dam Height |
24 |
River Or Stream |
JAKES CREEK |
Primary Dam Type |
Earth |
Surface Area |
15 |
Hydraulic Height |
24 |
Drainage Area |
1 |
Nid Storage |
254 |
Structural Height |
26 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
26 |
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 G-18a