Every five years, the EPA coordinates the National Lakes Assessment (NLA), an intensive sampling event for lakes across the country. Teams visit a group of randomly selected locations representing a cross-section of lakes in each state.  While there, they collect samples for nutrients and to examine biological communities.  They also make observations to characterize physical aspects of the lake.  Teams spend one to several days completing the evaluation.  Samples are then sent to a central laboratory for processing.

With this data, EPA can evaluate, at a statewide and regional level, the condition of lakes across the country. (The assessment is not designed to evaluate the condition of an individual lake.)  In 2007, NLA observations about shoreland condition in Vermont and littoral habitat data that lake scientists in the VT Watershed Management Division had been collecting led to the adoption of the Vermont Shoreland Protection Act.

This week, EPA released the 2012 National Lakes Assessment Report.  Key findings were

  • 35% of lakes nationwide have too much nitrogen.
  • 40% of lakes nationwide have too much phosphorus
    • Additional studies comparing 2007 data to 2012 indicated that the number of lakes with low phosphorus levels has declined by 18% nationwide
  • 31% of lakes nationwide show impacts to the benthic macroinvertebrate community.
    • The number of lakes with moderately disturbed shoreline has increased since 2007 (see figure below.)

Here in Vermont, scientists in the Lakes and Ponds program will be digesting these results and considering what they tell us about our lakes. (Read about the results of the 2007 National Lake Assessment in Vermont.)  Though the National Lake Assessment can’t provide information about specific lakes, it can bring state, regional and national trends to light that connect directly to our efforts to protect Vermont lakes.