Diagnosing the Nation’s Streams

In March, EPA released results of its National Rivers and Stream Assessment. In some ways it makes for depressing reading-it shows that more than half the streams in the US are in bad shape. But there are some encouraging bits hidden in the report, too, or at least indications that we’re moving in the right direction to remedy the problems.

The data are from a survey conducted in 2008 and 2009, the most recent nationwide information available; more than 2,000 sites across the country were sampled. Overall, EPA’s report shows 55% of stream miles are in “poor condition” to support aquatic life. The report breaks that number down into more useful pieces.

High levels of nutrients, which can lead to excess algae growth and oxygen depletion, are the biggest problem. According to the survey, 27% of streams have excessive levels of nitrogen and 40% have excessive phosphorus. Major sources of nutrients are fertilizers from landscaping, golf courses, and agriculture.

Nearly a quarter of streams and rivers suffer from “decreased vegetation cover and increased human disturbance,” a broad category that leads to several different problems-making streams more likely to erode, allowing more pollutants to reach the streams, and increasing water temperature. The good news here, though, is that the national Construction General Permit released in February 2012 addresses this problem. It calls for a 50-foot natural buffer between construction activity and surface waters-or, in cases where that isn’t possible because of a narrow right of way, it calls for added erosion and sediment control measures to achieve a reduction in sediment load similar to that of a 50-foot buffer. Although the national CGP applies directly only in the states that don’t have their own CGP, most states look to it when revising and updating their own, and the 2012 provisions are likely to trickle down, so to speak.

Other findings from the survey: about 9% of streams and rivers have high levels of bacteria, and in 13,000 miles of rivers, fish show excessively high levels of mercury. And 15% of streams suffer from excessive streambed sediments-a respectable number, when you consider that just a few years ago EPA ranked sediment as the number one surface water pollutant.

Of course, the big picture indicated by these numbers isn’t necessarily useful in your part of the world-the problems in your streams and rivers have site-specific causes and need specific and well-thought-out solutions. But the survey does give us a snapshot of how policy is affecting stream health, and an idea of what we’re doing right.