Algonquin Dam Reservoir Report

Last Updated: December 13, 2025

Algonquin Dam, located on the Fox River in Algonquin, Illinois, serves as a critical structure for flood risk reduction in the area.


°F

°F

mph

Wind

%

Humidity

Summary

Completed in 1947, this concrete dam stands at a height of 9 feet and spans 300 feet in length. With a storage capacity of 24,200 acre-feet, the dam plays a key role in managing water levels and mitigating flood risks along the river.

Managed by the Illinois Department of Natural Resources, Algonquin Dam is subject to state regulation and inspection to ensure its structural integrity and operational efficiency. While primarily designed for flood risk reduction, the dam also provides opportunities for recreation in the surrounding area. Despite its age, the dam's hazard potential is deemed significant, highlighting the importance of ongoing monitoring and maintenance to ensure public safety and environmental protection.

As part of the Chicago District, Algonquin Dam is overseen by state authorities and operates with an uncontrolled spillway type. While its condition assessment is currently unavailable, the dam's risk assessment is moderate, indicating a need for continued monitoring and risk management measures. With its historical significance and vital role in water resource management, Algonquin Dam stands as a testament to the importance of infrastructure in safeguarding communities against natural disasters and climate impacts.

Year Completed

1947

Dam Length

300

Dam Height

9

River Or Stream

FOX RIVER

Primary Dam Type

Concrete

Nid Storage

24200

Outlet Gates

None

Hazard Potential

Significant

Foundations

Unlisted/Unknown

Nid Height

9
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No 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

High
Dams 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.