Lakes and reservoirs provide many environmental, economic, and public health benefits. We use lakes for drinking water, energy production, food, and recreation, while fish, birds, and other wildlife rely on them for habitat and survival. In the National Lakes Assessment (NLA), the U.S. Environmental Protection Agency (EPA) and its partners surveyed a wide array of lakes representative of those found in the U.S., from small ponds and prairie potholes to large lakes and reservoirs.
The National Lakes Assessment 2012: A Collaborative Survey of the Lakes in the United States presents the results of a second evaluation of the biological, chemical, physical, and recreational condition of lakes in the United States, the first having been conducted in 2007. During spring and summer of 2012, 89 field crews sampled 1,038 lakes across the country. Each field crew used consistent procedures to sample benthic macroinvertebrates (e.g., insect larvae, snails, and clams), zooplankton (small animals in the water column), algal toxins, atrazine, and nutrients and to observe near-shore habitat so that results could be compared across the country. These measured values were compared to NLA benchmarks, which are points of reference used to determine the proportion of lakes that are relatively high quality (least disturbed), medium quality (moderately disturbed), and degraded (most disturbed) in condition.