EPA National Lakes Assessment

During the summer of 2012, the U.S. Environmental Protection Agency (EPA), states, tribes and other partners conducted the second nationwide survey of the condition of the nation’s lakes. Designed to estimate the percentage of lakes that are in good, fair, or poor condition, the National Lakes Assessment (NLA) serves as a scientific report card on America’s lakes. It examines ecological, water quality, and recreational indicators, and assesses how widespread key stressors (such as nitrogen, phosphorus, and acidification) are across the country. The intention of the NLA is to help build state and tribal capacity for monitoring and assessment, and to promote collaboration across jurisdictional boundaries in the assessment of water quality.

The NLA provides statistically valid regional and national estimates of the condition of lakes, using a probability-based sampling design to represent the condition of all lakes in similar regions sharing ecological characteristics. The assessment took samples from 904 sites nationwide. Data were collected on algal toxins, benthic macro-invertebrates, Chlorophyll A, nutrients, phytoplankton, sediment dating, sediment diatoms, sediment mercury, water chemistry, and zooplankton.

Climate change impacts on lakes are discussed in the "Highlights" section of the 2007 NLA. The first assessment described how climate change has already increased water temperatures affecting lake conditions; caused evaporation, algal blooms and reduced fish populations in the Great Lakes; and caused temperature, precipitation and extreme weather effects on Lake Tahoe and Lake Mead.   

The EPA NLA website also includes the NLA Site Evaluation Guidelines, Field Operation Manual, Lab Operations Manual, and a Quality Assurance Project Plan.


 If you have any trouble accessing the website link above, please find here an archived page. You may find this has limited use. https://web.archive.org/web/20170105162656/https://www.epa.gov/national-aquatic-resource-surveys/national-lakes-assessment-2012-results 



Publication Date: 2012

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  • Assessment


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