Thomson Reservoir is a 339-acre impoundment located north of Thomson, Minnesota, operated by Minnesota Power for hydroelectric generation. The reservoir features 11 miles of shoreline and reaches a maximum depth of 22 feet, with 83% of the water body being less than 15 feet deep.

Access is limited to a carry-down site at the north end of Thomson's main street. A planned expansion of the Kayak Center parking lot will improve access for recreational paddlers. The reservoir serves as a take-out point for whitewater paddlers traveling downstream from Scanlon on the St. Louis River.

The reservoir's water levels are subject to manipulation for power generation purposes. Multiple islands and rocky, boreal forest-covered shoreline provide scenic paddling opportunities. The Midway River flows into the reservoir, creating additional areas to explore. Paddlers can spend several hours investigating the various islands, scenic shoreline, and river mouth areas.

The reservoir supports diverse wildlife and fish populations, including smallmouth bass, walleye, northern pike, and yellow perch. The surrounding landscape includes Jay Cooke State Park, offering additional recreational opportunities.

Currently, the reservoir is undergoing an environmental remediation project to address historical contamination from industrial discharges, specifically dioxins and furans in the sediment. The project, scheduled for 2024, will treat approximately 69 acres of the reservoir but should not significantly impact recreational access.

For paddlers seeking a full day of exploration, nearby water bodies include Scanlon Reservoir (3.2 miles away) and Knife Falls Reservoir (4.2 miles away). The reservoir's location near Carlton provides convenient access to local amenities and services.