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A total of 9,139 lakes in the Southern Appalachians ecoregion are represented in the NLA. Of these lakes, less than 1% are natural and over 99% 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 Appalachians, 26% of lakes are rated as most disturbed based on trophic state, 46% are eutrophic, 11% are mesotrophic, and 18% are oligotrophic.
• The most widespread stressors assessed are phosphorus (67% of lakes), nitrogen (63%), and riparian vegetation cover (52%).

• Trophic State

  

• Indicator with the Highest Percentage of Lakes in the Most Disturbed Condition: Phosphorus

  

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.

Oklahoma lake sampled during the NLA 2012. Photo: Jessie Stine. 

• Based on cyanobacteria cell counts, 18% of lakes in the Southern Appalachians are in the most disturbed condition (i.e., pose a high risk of exposure to algal toxins).

Change from 2007 (for lakes >4 hectares)*:

• For the Southern Appalachians, the NLA reports a 24% increase in the proportion of lakes in most disturbed condition between 2007 and 2012 based on the condition of cyanobacteria risk.

• Percentage of Lakes in Most Disturbed Condition for all Indicators: Southern Appalachians

  

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

* 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.