Thomson Reservoir Report

Last Updated: December 5, 2025

Thomson is a hydroelectric dam located on the St.


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Summary

Louis River in Carlton, Minnesota. Built in 1907, it stands at a height of 15 feet and has a length of 1600 feet. The dam has a storage capacity of 4352 acre-feet and covers a surface area of 375 acres, with a drainage area of 3548 square miles. With a maximum discharge of 91700 cubic feet per second, Thomson plays a crucial role in both hydroelectric power generation and recreation.

Owned by the Federal Energy Regulatory Commission (FERC), Thomson is regulated by both state and federal agencies, including the Minnesota Department of Natural Resources. The dam is inspected regularly to ensure its safety, with a high hazard potential due to its location and structure. Emergency action plans are in place, with an updated contact list and risk assessment indicating a high level of risk management measures. Thomson's primary purpose is hydroelectric power generation, with associated structures and outlet gates for efficient operation.

Thomson offers a glimpse into the intersection of water resource management and climate considerations. As a key player in renewable energy production and water storage, this dam showcases the importance of balancing ecological impact with energy generation. With its historical significance and ongoing regulatory oversight, Thomson serves as a model for sustainable hydroelectric infrastructure in the face of changing climate patterns and increasing water demands.

Year Completed

1907

Dam Length

1600

Dam Height

15

River Or Stream

St Louis River

Surface Area

375

Hydraulic Height

15

Drainage Area

3548

Nid Storage

4352

Structural Height

15

Outlet Gates

Slide (sluice gate) - 3, Tainter (radial) - 14

Hazard Potential

High

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.