Upper Midwest Ecoregion - National Lakes Assessment Results
Key Results
An estimated 29,620 lakes in the Upper Midwest ecoregion are represented in the National Lakes Assessment (NLA). Of these lakes, 98% are natural and 2% 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, 14% of lakes are rated as hypereutrophic while 42% are eutrophic, 31% are mesotrophic and 12% are oligotrophic.
- The most widespread stressors assessed are atrazine detections, nitrogen and phosphorus with 43%, 24% and 20% of lakes in poor condition respectively.
- 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.
Change from 2012*
- For the Upper Midwest, the NLA reports that the percent of lakes in good condition for phosphorus increased by 29 percentage points between 2012 and 2017 and for habitat complexity by 21 percentage points.
- The percent of lakes that are hypereutrophic increased by 9 percentage points between 2012 and 2017.
- The percent of lakes with microcystins detections decreased by 19 percentage points.
To access more ecoregional specific information, please visit the interactive NLA Dashboard.
* The change analysis is based on information from two points in time – 2012 and 2017.
![Image showing the dashboard results from the NLA Interactive Dashboard](/system/files/styles/large/private/images/2022-06/UMW_2017_Good.png?itok=gU2GR3rf)