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Water: Lakes

National Lakes Assessment

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.


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.

Fact Sheets

NLA 2007 Fact Sheet: Summary Results of the First National Lakes Assessment (2 pp, 167K, About PDF)
NLA 2012 Fact Sheet: Overview of the Second National Lakes Assessment (2 pp, 352K, About PDF)

NLA 2012
  • Number of Sample Sites: 904
  • Revisit Sites: 96
Types of Sites:

The following map displays the base, oversample, and state supplemental sites that may be sampled during the 2012 NLA Field Season.

  • Base - The original 904 sites selected to be surveyed
  • Oversample - Sites that will substitute for the base sites if determined unsuitable for the survey (not in design, not reachable, not sampleable)
  • State Supplemental - some states had the ability to add on additional sample sites for state-scale surveys, these are the additional sites
NLA 2007


NLA 2012
NLA 2007


Data are being collected for the following indicators: Algal Toxins, Benthic Macroinvertebrates, Chlorophyll A, Nutrients, Phytoplankton, Sediment Dating, Sediment Diatoms, Sediment Mercury, Water Chemistry, and Zooplankton.


Data collected for each parameter sampled in the 2007 National Lakes Assessment (NLA) are available for downloading at the following link: 

National Lakes Assessment Data

The following planning tasks were part of the 2012 NLA:

  • Site Evaluation - States are evaluating sites for the NLA to determine if they are "target;" this will be ongoing throughout field season.
  • Manual Development - Field Operations Manual, Lab Operations Manual, and Quality Assurance Project Plan are completed.
  • Indicator Decision Making - Determining what indicators will be used for this next round of the 2012 NLA is completed.
  • Logistical Planning - Setting up contracts for logistics is completed
  • Electonic Field Form Development - Electronic field forms are being utilized this summer for field sampling with success.
  • Lab Verification - Reviewed the quality assurance protocols of labs that are participating in lab analysis this season.

The EPA conducts the National Lakes Assessment in collaboration with states, tribes, and other federal agencies. In addition to partnering on the national survey, many states choose to augment the selection of lakes sampled within their boundaries to assemble a statistically-valid picture of the lakes in their state.

NLA 2007

Examples of state-wide statistical surveys:

Other Surveys/Studies:

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