Blackhawk Lake Reservoir Report

Last Updated: December 13, 2025

Blackhawk Lake, located in Iowa, Wisconsin, is a picturesque water resource managed by the local government for recreational purposes.


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Summary

Built in 1969, this earth dam stands at a height of 50 feet, with a hydraulic height of 42 feet and a structural height of 50 feet. The reservoir has a storage capacity of 7,900 acre-feet, with a normal storage level of 3,810 acre-feet, covering a surface area of 220 acres.

Maintained by the Wisconsin Department of Natural Resources, Blackhawk Lake boasts controlled spillways and a low hazard potential, with a fair condition assessment as of May 2020. Despite its risk assessment being classified as very high, the dam has not undergone significant modifications over the years. The surrounding area is at a low risk of inundation, and the dam meets regulatory guidelines for inspection and enforcement.

With its serene surroundings and ample recreational opportunities, Blackhawk Lake is a beloved destination for water resource and climate enthusiasts to explore and appreciate the beauty of its Otter Creek and Cave Hollow Branch tributaries. Its rich history, steady water levels, and well-maintained infrastructure make it a valuable asset for the community and a must-visit spot for those interested in water conservation and outdoor activities in the heart of Wisconsin.

Year Completed

1969

Dam Length

1130

Dam Height

50

River Or Stream

OTTER CREEK & CAVE HOLLOW BR

Primary Dam Type

Earth

Surface Area

220

Hydraulic Height

42

Drainage Area

16.1

Nid Storage

7900

Structural Height

50

Hazard Potential

Low

Nid Height

50
       
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.