Northern Plains Ecoregion - National Lakes Assessment Results

An estimated 11,146 lakes in the Northern Plains ecoregion are represented in the National Lakes Assessment (NLA). Of these lakes, 34% are natural and 66% 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 Northern Plains, 36% of lakes are rated as hypereutrophic while 31% are eutrophic, 29% are mesotrophic and 1% are oligotrophic.
• The most widespread stressors assessed are degraded riparian vegetation cover and nitrogen with 79%, and 80%  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.
  • Based on microcystins, detections occurred in 51% of lakes and 4% of lakes were above the recreational benchmark.

Change from 2017*

• For the Northern Plains, the NLA reports that the percent of lakes in good condition for lakeshore disturbance decreased by 9 percentage points between 2017 and 2012.
• The percent of lakes in poor condition for phosphorus decreased by 12 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 – 2017 and 2022.