Stephen A. Forbes State Park Lake Dam Reservoir Report
Nearby: Marlow Pond Dam Greendale Lake Dam
Last Updated: December 5, 2025
Stephen A.
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Summary
Forbes State Park Lake Dam, located in Marion, Illinois, is a captivating site for water resource and climate enthusiasts. Built in 1963, this earth dam stands at a height of 46 feet and stretches for 1335 feet, creating a reservoir with a maximum storage capacity of 15,739 acre-feet. The dam serves the primary purposes of recreation and water supply, offering a serene setting for outdoor activities and a vital resource for the surrounding area.
The dam's spillway, with a width of 340 feet, is uncontrolled, allowing for the safe release of excess water during periods of high flow. The dam is regulated by the Illinois Department of Natural Resources (IDNR) and undergoes regular inspections to ensure its structural integrity and safety. With a significant hazard potential and moderate risk assessment, the dam plays a crucial role in managing water resources in the region while providing recreational opportunities for visitors to Stephen A. Forbes State Park.
Surrounded by the natural beauty of Lost Fork Creek and covering a surface area of 585 acres, Stephen A. Forbes State Park Lake Dam is a vital part of the local ecosystem. With a drainage area of 21.1 square miles and a maximum discharge capacity of 30,848 cubic feet per second, this dam is a key feature for water management in the area. Enthusiasts interested in water resource management and climate resilience will find Stephen A. Forbes State Park Lake Dam to be a fascinating structure that blends functionality with natural beauty, making it a must-visit destination for those passionate about water systems and their impact on the environment.
Year Completed |
1963 |
Dam Length |
1335 |
Dam Height |
46 |
River Or Stream |
LOST FORK CREEK |
Primary Dam Type |
Earth |
Surface Area |
585 |
Drainage Area |
21.1 |
Nid Storage |
15739 |
Outlet Gates |
Uncontrolled |
Hazard Potential |
Significant |
Foundations |
Unlisted/Unknown |
Nid Height |
46 |
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.
Stephen A. Forbes State Park Lake Dam