Williamsville Lake Dam 1 Reservoir Report
Last Updated: December 20, 2025
Williamsville Lake Dam 1, located in Petersburg, Illinois, was completed in 1971 and is regulated by the Illinois Department of Natural Resources.
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Summary
The dam, designed by USDA NRCS, is primarily used for recreational purposes and has a low hazard potential. With a height of 23 feet and a length of 600 feet, the earth dam holds a maximum storage capacity of 180 acre-feet and covers a surface area of 18 acres.
Situated on Wolf Creek in Sangamon County, the dam features an uncontrolled spillway with a width of 20 feet and outlet gates that are also uncontrolled. The dam's drainage area is 0.39 square miles, with a maximum discharge capacity of 165 cubic feet per second. Despite its moderate risk assessment rating, the dam has not undergone a recent condition assessment and lacks an Emergency Action Plan (EAP).
With its picturesque setting and recreational opportunities, Williamsville Lake Dam 1 presents a notable landmark in the St. Louis District. As water resource and climate enthusiasts, it is important to monitor the dam's condition and ensure that appropriate risk management measures are in place to safeguard the surrounding community and environment.
Year Completed |
1971 |
Dam Length |
600 |
Dam Height |
23 |
River Or Stream |
WOLF CREEK |
Primary Dam Type |
Earth |
Surface Area |
18 |
Drainage Area |
0.39 |
Nid Storage |
180 |
Outlet Gates |
Uncontrolled |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
23 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Sangamon River At Riverton
|
125cfs |
Lake Fork Near Cornland
|
17cfs |
Spring Creek At Springfield
|
7cfs |
South Fork Sangamon River Nr Rochester
|
11cfs |
Salt Creek Near Greenview
|
204cfs |
Sangamon River At Petersburg
|
209cfs |
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.
Williamsville Lake Dam 1