Ganzhorn Dam Reservoir Report

Last Updated: December 13, 2025

Ganzhorn Dam, located in Harrison County, Iowa, was completed in 1970 and is primarily used for fire protection, stock, and as a small fish pond.


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Summary

The dam is privately owned and regulated by the Iowa Department of Natural Resources. It stands at a height of 30 feet and has a length of 356 feet, with a storage capacity of 60 acre-feet and a surface area of 4 acres. The dam is classified as an earth dam with a soil foundation, and its primary purpose is to provide essential services to the surrounding area.

The dam's hazard potential is rated as low, with a moderate risk assessment score of 3. While the condition of the dam is currently not rated, it is regularly inspected by state authorities to ensure its safety and functionality. Ganzhorn Dam does not have an Emergency Action Plan (EAP) in place, and its risk management measures are not specified. The dam's spillway type is uncontrolled, and it does not have outlet gates or locks associated with it.

Despite its modest size and purpose, Ganzhorn Dam plays a crucial role in providing water resources for fire protection and livestock in the area. As climate change continues to impact water availability and quality, it is essential to monitor and maintain dams like Ganzhorn to ensure their resilience and effectiveness in the face of changing environmental conditions.

Year Completed

1970

Dam Length

356

Dam Height

30

River Or Stream

TR-WILLOW CREEK

Primary Dam Type

Earth

Surface Area

4

Drainage Area

0.22

Nid Storage

60

Hazard Potential

Low

Foundations

Soil

Nid Height

30
       
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.