An official website of the United States government.

We've made some changes to EPA.gov. If the information you are looking for is not here, you may be able to find it on the EPA Web Archive or the January 19, 2017 Web Snapshot.

National Aquatic Resource Surveys

Southern Plains Ecoregion - National Lakes Assessment 2012 Results


Key Results

A total of 7,734 lakes in the Southern Plains ecoregion are represented in the National Lakes Assessment (NLA). Of these lakes, about 10% are natural and 90% are man-made.  

Trophic State and Key Stressors 

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

  • In the Southern Plains, 45% of lakes are rated as most disturbed based on trophic state, 17% are eutrophic, 36% are mesotrophic, and 2% are oligotrophic.
  • The most widespread stressors assessed are nitrogen (61% of lakes), phosphorus (58%), and lake habitat complexity (31%).

Top of Page


    Photo of a lake in the Southern Plains ecoregion that was sampled during the National Lakes Assessment 2012NLA 2012 sampling in Blue Lake, Kansas.

    Human Use Condition

    Cyanobacteria is one of three algal toxin related indicators presented in the NLA (see also chlorophyll a and microcystins). It serves as a proxy for the presence of algal toxins.

    • Based on cyanobacteria cell counts, 19% of lakes in the Southern Plains are in the most disturbed condition (i.e., pose a high risk of exposure to algal toxins).

    Top of Page


    Change from 2007 (for lakes >4 hectares)*

    • For the Southern Plains, the NLA reports a 34% increase in the proportion of lakes in most disturbed condition between 2007 and 2012 based on the condition of chlorophyll a risk.

    To access more indicator graphics please visit the interactive NLA Dashboard.

    Top of Page

    * The change analysis is based on information from two points in time – 2007 and 2012.  The change in condition analysis only considers lakes 4 hectares and larger because smaller lakes were not sampled in 2007.