Siem Lake Dam Reservoir Report
Last Updated: December 16, 2025
Siem Lake Dam, located in St.
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Summary
Charles, Missouri, serves as a crucial flood risk reduction structure along the TR-Missouri River. Completed in 1973, this earth dam stands at a height of 23 feet and spans 600 feet in length, providing a storage capacity of 135 acre-feet. The dam also caters to recreational activities, fish and wildlife preservation, and flood risk mitigation in the region.
Despite its significant hazard potential, Siem Lake Dam has not been rated for its condition assessment. The spillway, with a width of 20 feet, serves as an uncontrolled release point for excess water during times of high discharge. This structure, funded and operated privately, plays a vital role in managing the local drainage area of 106 square miles and stands as a symbol of partnership between private ownership and community flood risk reduction efforts.
With a moderate risk assessment rating, Siem Lake Dam continues to be a focal point of water resource management in the region. As water resource and climate enthusiasts, it is imperative to recognize the importance of maintaining and monitoring such structures to safeguard against potential hazards and ensure sustainable use of our water resources for generations to come.
Year Completed |
1973 |
Dam Length |
600 |
Dam Height |
23 |
River Or Stream |
TR-MISSOURI RIVER |
Primary Dam Type |
Earth |
Surface Area |
1 |
Hydraulic Height |
23 |
Drainage Area |
106 |
Nid Storage |
135 |
Structural Height |
23 |
Outlet Gates |
None |
Hazard Potential |
Significant |
Foundations |
Soil |
Nid Height |
23 |
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.
Siem Lake Dam
Downtown Washington