Upper Midwest Ecoregion - National Lakes Assessment Results

• Key results
• Change from 2017

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Key Results

An estimated 33,024 lakes in the Upper Midwest ecoregion are represented in the National Lakes Assessment (NLA). Of these lakes, 94% are natural and 6% are man-made.

The NLA uses trophic state as an important indicator of lake condition and assesses the extent of biological condition and key stressors in the nation’s lakes.

• In the Upper Midwest, 22% of lakes are rated as hypereutrophic while 38% are eutrophic, 36% are mesotrophic and 3% are oligotrophic.
• The most widespread stressors assessed are microcystin detections with 42% of lakes having microcystin detections and phosphorus with 41% of lakes in poor condition.
• Cyanobacteria are one-celled photosynthetic organisms that normally occur at low levels. Under eutrophic conditions, cyanobacteria can multiply. Not all cyanobacterial blooms are toxic, but some may release toxins, such as microcystins. For information about risks at specific locations, recreational water users should check with state, tribal or local governments.
  • Based on microcystins, detections occurred in 42% of lakes and 1% of lakes were above the recreational benchmark.

    

To access more ecoregional specific information, please visit the interactive NLA Dashboard.

* The change analysis is based on information from two points in time – 2017 and 2022.