Portland Reservoir Report

Last Updated: December 5, 2025

Located in Lyons, Michigan, the Portland Hydroelectric Dam on the Grand River is a historic structure with a rich history dating back to its completion in 1919.


°F

°F

mph

Wind

%

Humidity

Summary

Designed by AYERS, LEWIS, NORRIS AND MAY from Ann Arbor, MI, this dam serves multiple purposes, including hydroelectric power generation and recreation. With a dam height of 9 feet and a structural height of 15 feet, it has a storage capacity of 117 acre-feet and a maximum discharge of 2400 cubic feet per second.

Operated by the Federal Energy Regulatory Commission, the Portland Dam is classified as having a low hazard potential, with a moderate risk assessment rating. The dam has an uncontrolled spillway with a width of 325 feet, ensuring proper water flow management during high water events. While the condition assessment of the dam is currently not available, regular inspections are conducted every three years to ensure its structural integrity and safety.

The Portland Dam plays a vital role in the water resource management of the region, providing both environmental benefits and recreational opportunities for the community. As a popular spot for outdoor enthusiasts, the dam contributes to the local economy and serves as a reminder of the importance of sustainable water resource management in the face of changing climate conditions.

Year Completed

1919

Dam Length

680

Dam Height

9

River Or Stream

Grand River

Surface Area

30

Hydraulic Height

11

Drainage Area

1700

Nid Storage

186

Structural Height

15

Hazard Potential

Low

Foundations

Soil

Nid Height

15
       
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.