Gannon Dam Reservoir Report

Last Updated: December 11, 2025

Gannon Dam, located in Jasper County, Iowa, was completed in 1969 and serves multiple purposes including fire protection, stock watering, and small fish pond recreation.


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Summary

Owned privately, the dam is regulated by the Iowa Department of Natural Resources and is subject to state permitting, inspection, and enforcement. The dam, designed by the USDA NRCS, is an earth structure with a height of 27 feet and a length of 300 feet, providing a storage capacity of 48 acre-feet and covering a surface area of 3 acres.

Situated on the TR-Skunk River, Gannon Dam has a low hazard potential and a moderate risk assessment rating. Its spillway type is uncontrolled, and it has not been modified in recent years. Although the dam's condition has not been formally assessed, it is deemed to be in a satisfactory state. While the dam does not fall under the jurisdiction of the US Army Corps of Engineers, it is subject to state regulations and oversight, ensuring its safe operation and maintenance for the surrounding community and ecosystem. Water resource and climate enthusiasts can appreciate the role of Gannon Dam in providing essential services while managing potential risks associated with its operation.

Year Completed

1969

Dam Length

300

Dam Height

27

River Or Stream

TR-SKUNK RIVER

Primary Dam Type

Earth

Surface Area

3

Drainage Area

0.17

Nid Storage

48

Hazard Potential

Low

Foundations

Soil

Nid Height

27
       
Seasonal Comparison

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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.