The National Lakes Assessment reveals that the remaining lakes are in fair or poor condition. Degraded lakeshore habitat, rated “poor” in 36% of lakes, was the most significant of the problems assessed. Removal of trees and shrubs and construction of docks, marinas, homes and other structures along shorelines all contribute to degraded lakeshore habitat.

Nitrogen and phosphorous are found at high levels in 20% of lakes. Excess levels of these nutrients contribute to algal blooms, weed growth, reduced water clarity, and other lake problems. EPA is very concerned about the adverse impacts of nutrients on aquatic life, drinking water and recreation. The agency will continue to work with states to address water quality issues through effective nutrient management. 

The survey included a comparison to a subset of lakes with wastewater impacts that were sampled in the 1970s. It finds that 75% show either improvements or no change in phosphorus levels. This suggests that the nation’s investments in wastewater treatment and other pollution control activities are working despite population increases across the country. 

The results of this study describe the target population of the nation’s lakes as a whole and are not applicable to a particular lake. 

Sampling for the National Rivers and Streams Assessment is underway, and results from this two-year study are expected to be available in 2011.