First-Ever Assessment of U.S. 'Wadeable' Streams Finds Almost Half In Poor Condition
The first consistent evaluation of the streams that feed rivers, lakes, and coastal waters finds that 28 percent of U.S. stream miles are in good condition compared to the best available reference sites in their regions, 25 percent are in fair condition, and 42 percent are in poor condition.
On May 5, EPA released results from its multiyear study, the Wadeable Streams Assessment, of streams that feed rivers, lakes, and coastal waters. "Wadeable streams" are those which are shallow enough to be adequately sampled without a boat. They are essential natural resources that have been under-sampled in the past, according to EPA.
"This scientific report card on America's streams will help citizens and governments measure the health of their watersheds, take actions to prevent pollution, and monitor for progress," said Assistant Administrator for Water Benjamin H. Grumbles. "Small streams are connected to the overall health of a community's ecology and economy and this report underscores their importance and identifies priority work ahead."
The assessment was designed using modern survey techniques, 1,392 random sites were sampled to represent the condition of all streams in regions that share similar ecological characteristics. Participants used the same standardized methods at all sites, to ensure results that are comparable across the nation. A rigorous quality control program included training all field crews, auditing field crews and labs, and re-sampling 10 percent of the sites. The sampling began with pilot work in the West in 2000 and was completed nationwide in 2004.
Alaska and Hawaii were not included in the report but have pilot projects underway.
The WSA measured key chemical and physical indicators that reveal stress, or degradation of streams. The most widespread stressors observed are nitrogen, phosphorus, and streambed sediments, which smother aquatic habitat and degrade conditions for fish. Nitrogen and phosphorus are nutrients that can increase the growth of algae, decrease levels of dissolved oxygen and cloud the water.
The study determined that stream quality varies widely across the diverse ecological regions of the United States. The western region of the country is in the best condition, with 45 percent of the length of wadeable streams and rivers in good condition. In the eastern highlands region, 18 percent of stream length is in good condition and more than half is in poor condition. The quality of streams in the plains and lowlands region falls between the other two regions, with almost 30 percent of stream length in good condition and 40 percent in poor condition. See figure 1 in the "The Wadeable Streams Assessment Fact Sheet" (http://www.epa.gov/owow/monitoring/wsa/WSAfactsheet_0506.pdf) for a map outlining the regions and their stream conditions.
The study is part of a series of surveys to evaluate all of the nation's waters. Coastal condition has already been evaluated. During the next five years, EPA will sample the condition of lakes, large rivers, and wetlands. Then the process will be repeated to provide ongoing comparisons of the state of the waters and point to possible future action.
For additional information on the assessment, go to http://www.epa.gov/owow/streamsurvey.
This article originally appeared in the 05/01/2006 issue of Environmental Protection.