Portage Lake Dam Reservoir Report

Last Updated: December 5, 2025

Located in Jackson, Michigan, the Portage Lake Dam stands as a vital structure for recreation purposes, offering a serene and picturesque environment for water resource and climate enthusiasts.


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Summary

Completed in 1957, this earth dam spans 3,200 feet in length and reaches a height of 7.5 feet, serving as a tributary to the Portage River. With a normal storage capacity of 5,000 acre-feet and a maximum discharge rate of 37 cubic feet per second, the dam provides essential water storage and flow regulation in the region.

Managed by the state of Michigan, the Portage Lake Dam is subject to periodic inspections, with its hazard potential rated as low and its overall condition assessed as fair. Despite its moderate risk assessment level, the dam continues to operate effectively, maintaining a strong structural integrity for the surrounding community. While the dam does not fall under federal jurisdiction, its presence contributes to the environmental health and recreational opportunities in the area, attracting visitors and wildlife alike to its tranquil waters.

As an integral part of the local landscape, the Portage Lake Dam serves as not only a functional structure but also as a symbol of the harmonious coexistence between human development and natural resources. With its controlled spillway and moderate risk management measures in place, the dam stands as a testament to responsible water resource management and the importance of maintaining a balance between conservation and recreation. For water resource and climate enthusiasts, the Portage Lake Dam offers a compelling glimpse into the intricate relationship between man-made infrastructure and the preservation of our natural environment.

Year Completed

1957

Dam Length

3200

Dam Height

7.5

River Or Stream

Tributary to Portage River

Primary Dam Type

Earth

Surface Area

400

Hydraulic Height

4.9

Drainage Area

4.73

Nid Storage

6500

Structural Height

7.5

Hazard Potential

Low

Nid Height

8
       
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.