Willow Lake Dam Reservoir Report
Nearby: Iowa Noname70 Ganzhorn Dam
Last Updated: December 13, 2025
Willow Lake Dam, located in Harrison County, Iowa, was completed in 1976 and is owned by the local government.
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Summary
The dam, designed by DESIGN ENGINEERING,INC., serves the primary purpose of debris control along the TR-WILLOW CREEK river or stream. With a height of 31 feet and a length of 390 feet, the earth dam has a storage capacity of 44 acre-feet and a surface area of 19 acres.
Managed by the Iowa Department of Natural Resources, Willow Lake Dam is regulated, inspected, and enforced by the state. The dam's hazard potential is rated as low, with a moderate risk assessment score. While the dam's condition is currently not rated, it meets the necessary guidelines for emergency action planning. The dam also provides recreational opportunities in addition to its debris control function.
Water resource and climate enthusiasts will appreciate the environmental impact and importance of Willow Lake Dam in managing water flow and debris along TR-WILLOW CREEK. As a key infrastructure in Harrison County, Iowa, the dam plays a crucial role in ensuring public safety and maintaining the ecological balance of the area. With its low hazard potential and moderate risk assessment, Willow Lake Dam stands as a testament to effective water resource management and engineering in the region.
Year Completed |
1976 |
Dam Length |
390 |
Dam Height |
31 |
River Or Stream |
TR-WILLOW CREEK |
Primary Dam Type |
Earth |
Surface Area |
19 |
Drainage Area |
0.21 |
Nid Storage |
44 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
31 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Soldier River At Pisgah
|
112cfs |
Boyer River At Logan
|
417cfs |
Little Sioux River Near Turin
|
1040cfs |
Monona-Harrison Ditch Near Turin
|
158cfs |
Maple River At Mapleton
|
323cfs |
Missouri River At Decatur
|
15200cfs |
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.
Willow Lake Dam