Heishman Dam Reservoir Report
Nearby: Nagel Dam Holiday Lake Dam
Last Updated: December 6, 2025
Heishman Dam, located in Marengo, Iowa, is a privately owned earth dam constructed in 2017 for the primary purpose of recreation.
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Summary
The dam stands at a height of 40 feet and has a length of 340 feet, creating a reservoir with a storage capacity of 112 acre-feet. Situated on a tributary to Walnut Creek, the dam covers a surface area of 7.3 acres and serves as a popular spot for outdoor activities such as fishing, boating, and picnicking.
Managed and regulated by the Iowa Department of Natural Resources, Heishman Dam has a low hazard potential and is currently rated as "Not Rated" in terms of condition assessment. The dam features a spillway width of 40 feet and is inspected, permitted, and enforced by the state authorities to ensure its safety and functionality. With its serene surroundings and ample recreational opportunities, Heishman Dam is a vital water resource for the community and a picturesque destination for water resource and climate enthusiasts to explore and appreciate.
Year Completed |
2017 |
Dam Length |
340 |
Dam Height |
40 |
River Or Stream |
Tributary to Walnut Creek |
Primary Dam Type |
Earth |
Surface Area |
7.3 |
Drainage Area |
0.24 |
Nid Storage |
112 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
40 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Richland Creek Near Haven
|
12cfs |
Walnut Creek Near Hartwick
|
13cfs |
Iowa River Near Belle Plaine
|
966cfs |
Salt Creek Near Elberon
|
42cfs |
Big Bear Creek At Ladora
|
36cfs |
Timber Creek Near Marshalltown
|
37cfs |
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.
Heishman Dam