Downing Dam Reservoir Report
Last Updated: December 12, 2025
Downing Dam, located in Union, Iowa, is a privately owned structure designed by the USDA NRCS and regulated by the Iowa DNR.
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Summary
Completed in 1994, the dam serves multiple purposes including fire protection and as a stock or small fish pond. With a height of 25 feet and a length of 407 feet, Downing Dam has a storage capacity of 64 acre-feet and a surface area of 4 acres, providing valuable water resources for the surrounding area.
The dam's low hazard potential is complemented by a moderate risk assessment, indicating a level of safety and security for the community. While the condition assessment is currently not rated, the dam is regularly inspected, maintained, and regulated by state authorities to ensure its structural integrity and functionality. With its strategic location on TR- Threemile Creek, Downing Dam plays a crucial role in water management and conservation efforts in the region, highlighting its significance for water resource and climate enthusiasts.
Despite its uncontrolled spillway type, Downing Dam's design and construction by the Natural Resources Conservation Service reflect a commitment to sustainable water management practices. The dam's proximity to Talmage and its association with fire protection and fisheries underscore its importance in supporting local ecosystems and agricultural activities. As a notable feature in the Rock Island District, Downing Dam stands as a testament to effective collaboration between private ownership, federal agencies, and state regulators in safeguarding water resources and enhancing climate resilience in Union, Iowa.
Year Completed |
1994 |
Dam Length |
407 |
Dam Height |
25 |
River Or Stream |
TR- THREEMILE CREEK |
Primary Dam Type |
Earth |
Surface Area |
4 |
Drainage Area |
0.34 |
Nid Storage |
64 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
25 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
South Raccoon River At Redfield
|
268cfs |
Raccoon River At Van Meter
|
1640cfs |
Middle Raccoon River At Panora
|
92cfs |
Raccoon River Near West Des Moines
|
1300cfs |
East Fork 102 River At Bedford
|
1cfs |
North River Near Norwalk
|
48cfs |
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.
Downing Dam