More than 4 of every 10 US lakes are in only fair or poor condition, according to EPA's first national assessment using consistent criteria.
Man-made lakes tend to be in far worse condition than their natural cousins. Half of the lakes are home to fish whose flesh contains health-threatening concentrations of mercury. More than one-quarter of the lakes potentially pose a threat from algal toxins.
The findings in the draft report, released Dec. 18, 2009, are based on a review of indicators for physical, chemical, and biological measures of water quality; condition of lakeshore and shallow water habitat; and ability to support selected recreational uses. A public comment period on the draft report closes Jan. 22, 2010.
During 2007 EPA evaluated more than 1,000 lakes that were selected to represent about 50,000 lakes in the lower 48 states (excluding the Great Lakes and Great Salt Lake). The findings for individual lakes aren't available. Instead, the agency grouped the results by nine ecoregions, which are defined through a combination of climate, vegetation, soil type, and geology.
The findings for each ecoregion allow you to paint a general picture of lakes of interest to your audience. That will provide some beneficial information, since there often are major differences between the regions. For instance, 91% of the lakes in the Upper Midwest were in good biological condition, compared to just 5% in the Northern Plains. Recreational conditions were by far the best in the WesternMountains and the Northern Appalachians, and the worst in the Northern Plains and Temperate Plains.
In addition to ecoregion comparisons, the states of IN, MI, MN, OK, TX, and WI had enough lakes sampled so that they can provide state-level findings. These are expected to be available soon from each state.
Along with the current information you can glean from this survey, the results are expected to serve as baseline information for future studies.
Results of a similar study of rivers and streams are expected to be available in 2011.