Cowles Dam Reservoir Report
Nearby: Simpson Dam Shields Lake Dam
Last Updated: December 11, 2025
Cowles Dam, located in Decatur, Iowa, is a privately owned structure with a primary purpose of fire protection, stock, or small fish pond.
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Summary
Built in 1991 by the USDA NRCS, this earth dam stands at a height of 31 feet and has a length of 550 feet, creating a reservoir with a storage capacity of 113 acre-feet. The dam is regulated by the Iowa DNR and is inspected regularly to ensure its safety and compliance with state regulations.
Cowles Dam is situated on TR-Marks Creek and serves as a vital water resource for the surrounding area, providing water for fire protection, stock, and recreational use. With a surface area of 8.3 acres and a drainage area of 0.25 square miles, the dam plays a crucial role in managing water flow and supporting the local ecosystem. Despite its low hazard potential, the dam is categorized as having a moderate risk level, indicating the importance of ongoing monitoring and risk management measures.
While the condition assessment of Cowles Dam is currently listed as "Not Rated," its risk assessment suggests a need for proactive measures to address potential hazards. As a key component of the water infrastructure in the region, the dam's operation and maintenance are essential for ensuring water security and environmental sustainability. Climate and water resource enthusiasts can appreciate the role of Cowles Dam in supporting the community and protecting the local ecosystem amid changing environmental conditions.
Year Completed |
1991 |
Dam Length |
550 |
Dam Height |
31 |
River Or Stream |
TR- MARKS CREEK |
Primary Dam Type |
Earth |
Surface Area |
8.3 |
Drainage Area |
0.25 |
Nid Storage |
113 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
31 |
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.
Cowles Dam