Allegan Reservoir Report

Last Updated: December 5, 2025

Allegan, also known as Calkins Bridge, is a gravity dam located in Allegan, Michigan, along the Kalamazoo River.


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Summary

The dam was completed in 1936 and serves the primary purpose of hydroelectric power generation. With a dam height of 30 feet and a hydraulic height of 19.5 feet, Allegan has a normal storage capacity of 17,200 acre-feet and a maximum discharge of 26,703 cubic feet per second.

Managed by the Federal Energy Regulatory Commission, Allegan is considered to have a low hazard potential and a very high risk assessment rating. The dam features a controlled spillway with a width of 120 feet and is equipped with six Tainter radial outlet gates. Despite its age, Allegan's condition assessment is currently listed as not available, and it undergoes inspections every three years. Overall, Allegan stands as a significant infrastructure for hydroelectric power production in the region, contributing to the sustainable management of water resources and climate considerations.

Year Completed

1936

Dam Length

1335

Dam Height

30

River Or Stream

Kalamazoo River

Primary Dam Type

Gravity

Surface Area

1600

Hydraulic Height

19.5

Drainage Area

1550

Nid Storage

20640

Structural Height

24.5

Outlet Gates

Tainter (radial) - 6

Hazard Potential

Low

Foundations

Soil

Nid Height

30
       
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.