Delavan Reservoir Report

Last Updated: December 5, 2025

Delavan, also known as Comus Lake, is a gravity dam located in the city of Delavan, Wisconsin, along Turtle Creek.


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Summary

Owned and regulated by the local government, this dam was completed in 1947 and primarily serves the purpose of recreation. With a height of 13 feet and a storage capacity of 850 acre-feet, Delavan Dam covers a surface area of 164 acres and has a drainage area of 67 square miles.

Despite being classified as having a low hazard potential and fair condition assessment, Delavan Dam is considered to have a very high risk due to its location and surrounding factors. The dam has a controlled spillway and a maximum discharge of 1490 cubic feet per second. While the last inspection was conducted in October 2011, with a scheduled frequency of every 10 years, the risk management measures and emergency action plans for the dam are not readily available. With its historical significance and importance for recreational activities, Delavan Dam remains a notable landmark in the water resource and climate enthusiast community.

Year Completed

1947

Dam Length

100

Dam Height

13

River Or Stream

TURTLE CREEK

Primary Dam Type

Gravity

Surface Area

164

Hydraulic Height

7

Drainage Area

67

Nid Storage

850

Structural Height

13

Hazard Potential

Low

Nid Height

13
       
Seasonal Comparison

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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.