National Lake Survey - General Lake Assessment


EPA and its state and tribal partners conducted a survey of the nation's lakes, ponds and reservoirs in 2007 and began a second survey in 2012. This National Lakes Assessment is designed to provide statistically valid regional and national estimates of the condition of lakes. It uses a probability-based sampling design to represent the condition of all lakes in similar regions sharing similar ecological characteristics. Consistent sampling and analytical procedures ensure that the results can be compared across the country. The National Lakes Assessment helps build state and tribal capacity for monitoring and assessment and promotes collaboration across jurisdictional boundaries in the assessment of water quality.


The National Lakes Assessment (NLA) is the first-ever baseline study of the condition of the nation’s lakes. It is the latest in a series of surveys of the nation’s aquatic resources being conducted by EPA and its state and tribal partners. The NLA provides unbiased estimates of the condition of natural and man-made freshwater lakes, ponds, and reservoirs greater than 10 acres and at least one meter deep. Using a statistical survey design, lakes were selected at random to represent the condition of the larger population of lakes across the lower 48 states. A total of 1,028 lakes were sampled for the NLA during summer 2007, representing the condition of about 50,000 lakes nationwide. The Great Lakes and Great Salt Lake were not included in the survey. Field crews collected samples using the same methods at all lakes to ensure that results can be compared across the country. Researchers processed and analyzed 680,000 measurements, including indicators of water quality such as nutrients, dissolved oxygen and algal density; biological indicators such as phytoplankton and zooplankton (algae and microscopic animals); recreational indicators such as algal toxins and pathogens; and physical habitat indicators such as lakeshore and shallow water habitat cover.


The 2012 National Lakes Assessment has just completed its field sampling season. In the spring, EPA and its partners held 9 field training sessions and trained 89 sampling crews. This sampling season will lead to the second national report on the condition of the nation's lakes, ponds, and reservoirs. Next steps in the process include: lab sample processing, data cleanup, and data analysis.

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National Lake Survey 2007