Island Lake Reservoir Report

Last Updated: December 12, 2025

Island Lake in Rusk, Wisconsin, is a picturesque reservoir on Swift Creek with a primary purpose of recreation.


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Summary

The dam, completed in 1875, is a gravity type standing at 11 feet tall and 35 feet long, providing a storage capacity of 10,200 acre-feet and a surface area of 1,222 acres. With a low hazard potential and fair condition assessment, Island Lake offers a moderate risk level, making it a popular destination for water and climate enthusiasts seeking outdoor adventures.

The dam is regulated by the Wisconsin Department of Natural Resources, with state permitting, inspection, and enforcement in place to ensure safety and compliance. The spillway, of uncontrolled type, has a width of 29 feet, allowing for a maximum discharge of 385 cubic feet per second. The area surrounding Island Lake is a haven for recreational activities such as fishing, boating, and hiking, attracting visitors to enjoy the natural beauty and tranquility of this water resource.

With its rich history dating back to the 19th century, Island Lake continues to be a treasured gem in Wisconsin, offering not only a source of recreational enjoyment but also a scenic haven for wildlife and nature lovers. As climate change impacts water resources globally, Island Lake stands as a reminder of the importance of preserving and protecting our natural environments for future generations to enjoy.

Years Modified

1945 - Other

Year Completed

1875

Dam Length

35

Dam Height

11

River Or Stream

Swift Creek

Primary Dam Type

Gravity

Surface Area

1222

Hydraulic Height

4

Drainage Area

29.3

Nid Storage

10200

Structural Height

11

Hazard Potential

Low

Nid Height

11
       
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.