Lake Superior

Lake Superior’s forested watershed and coastal wetlands help maintain water quality and a healthy aquatic ecosystem.

  • A cup with water in it. The caption reads “Be a source of safe, high quality drinking water”. The lake icon is green, indicating a status of Good.

    Be a source of safe, high quality drinking water.

  • A person swimming at the surface of the water with their arm over their head. The caption reads “Allow for unrestricted swimming and other recreational use”. The lake icon is green, indicating a status of Good.

    Allow for unrestricted swimming and other recreational use

  • A fish mid-jump. The caption reads “Allow for unrestricted human consumption of the fish and wildlife”. The lake icon is green, indicating a status of Good.

    Allow for unrestricted human consumption of the fish and wildlife

  • An industrial complex with smoke coming out of smokestacks. The caption reads “Be free from pollutants that could harm people, wildlife, or organisms”. The lake icon is green, indicating a status of Good.

    Be free from pollutants that could harm people, wildlife or organisms

  • A heron standing next to some trees. The caption reads “Support healthy and productive habitats to sustain our native species”. The lake icon is green, indicating a status of Good.

    Support healthy and productive habitats to sustain our native species

  • Two microorganisms next to each other. The caption reads “Be free from nutrients that promote unsightly or toxic blooms”. The lake icon is green, indicating a status of Good.

    Be free from nutrients that promote unsightly or toxic blooms

  • An invasive Carp and two dreissenid mussels with invasive Phragmites in the background. The caption reads “Be free from aquatic and terrestrial invasive species”. The lake icon is red on the left and green on the right, indicating a status of Poor to Good.

    Be free from aquatic and terrestrial invasive species

  • A pump with water dripping into cup. The caption reads “Be free from the harmful impacts of contaminated groundwater”. The lake icon is grey, indicating a status of No Trend.

    Be free from the harmful impacts of contaminated groundwater

  • A city skyline with a lake and waves in the foreground and rain and clouds in the sky. The caption reads “Be free from other substances, materials, or conditions that may negatively affect the Great Lakes”. The lake icon is green, indicating a status of Good.

    Be free from other substances, materials, or conditions that may negatively affect the Great Lakes

Status legend: Good (green), fair (yellow), poor (red)

Lake Superior’s treated drinking water is assessed as Good. It continues to be a reliable source for producing high quality drinking water. However, the indicator trend calculation is highly influenced by low sample size, with only 2 drinking water systems in Canada and 17 drinking water systems in the U.S. that source from Lake Superior surface waters. The U.S. 10-year trend for treated drinking water is assessed as Deteriorating due to violations of health-based standards reported at only two Community Water Systems (CWSs). Nonetheless, over 90% of CWSs met all health-based standards in nine of the last 10 years, underscoring Lake Superior’s continued provision of high-quality drinking water. Concentrations of many toxic chemicals monitored in Lake Superior are lower than in the other Great Lakes and long-term trends indicate that concentrations continue to decline. Lake Superior fish remain a nutritious food source; however, fish consumption advisories continue to be in effect for some species due to contaminant levels in fish fillets that exceed benchmarks. Overall, beaches and nearshore waters in Lake Superior provide good opportunities for swimming and recreational use, with only occasional beach closures or advisories posted.

Current nutrient levels are considered Good, with minimal short-lived, non-toxic blooms of cyanobacteria occurring in localized areas, such as between Duluth Harbor and the Apostle Islands. Coastal wetlands in the Lake Superior basin generally have healthy plant and fish communities and are in Good condition. The health of the lake is dependent on the health of the watersheds and the tributaries that connect them. Lack of habitat connectivity has reduced spawning habitat for some native fish species such as Lake Sturgeon, but conditions are Improving.

Lake Trout are fully recovered in most of the lake and are in Good condition, supported by a stable and diverse prey fish population. The lower food web is healthy with Phytoplankton, Zooplankton, and benthic communities in Good condition. Lake Superior’s prey fish community continues to have the highest proportion of native species of any of the Great Lakes. Populations of invasive Sea Lamprey remain above target levels to maintain fish community objectives and are still a major cause of mortality for native fish such as Lake Trout.

Groundwater quality, measured in terms of nitrate and chloride concentrations, has an Undetermined status and trend, given that there are limited data in the northern parts of the basin. The Lake Superior basin has a high percentage of natural land cover, which supports healthy habitats and water quality. However, the lake is experiencing changes such as warming surface waters and decreasing ice cover.

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