Lake Mendota Dam Reservoir Report
Last Updated: December 13, 2025
Lake Mendota Dam, located in Mendota, Illinois, serves as a crucial structure for the management of Mendota Creek.
°F
°F
mph
Wind
%
Humidity
Summary
Built in 1890, this Earth-type dam stands at a height of 17 feet and stretches over 2430 feet in length, providing a storage capacity of 246 acre-feet. While primarily designed for recreational purposes, the dam also plays a key role in regulating water flow and ensuring flood control in the area.
With a high hazard potential and a very high risk assessment rating, Lake Mendota Dam is closely monitored and inspected by the Illinois Department of Natural Resources. Despite its age, the dam has not undergone any recent modifications, and its condition assessment is currently listed as not available. The dam's controlled spillway and other controlled outlet gates help manage water levels and ensure the safety of the surrounding community in the event of an emergency.
As a significant landmark in LaSalle County, Illinois, Lake Mendota Dam stands as a testament to the engineering feats of the past and the ongoing importance of water resource management in the face of changing climate patterns. Its role in recreation, flood control, and water regulation underscores the critical need for continued monitoring and maintenance to ensure the safety and resilience of this vital infrastructure for years to come.
Year Completed |
1890 |
Dam Length |
2430 |
Dam Height |
17 |
River Or Stream |
MENDOTA CREEK |
Primary Dam Type |
Earth |
Surface Area |
17 |
Drainage Area |
221 |
Nid Storage |
246 |
Outlet Gates |
Other Controlled |
Hazard Potential |
High |
Foundations |
Unlisted/Unknown |
Nid Height |
17 |
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.
Lake Mendota Dam