According to an EPA study, only 28 percent of shallow or “wadeable” streams in the U.S., are in good shape. Streams in the East were ranked lowest, with 52 percent of those from the Appalachian Mountains to the Atlantic coast rated poor. Streams west of the Rock Mountains fared a little better.

Activities such as farming and logging can result in an increase in nitrogen and phosphorous levels in the water due to runoff. This leads to increased plant activity in these waters and a decrease in dissolved oxygen, which leads to decreases in aquatic life. Such conditions in the smaller streams can lead to dead zones in larger bodies of water, such as has been documented in the Gulf of Mexico.

“We passed the Clean Water Act 35 years ago, and this is the first time we've taken a look at our small rivers and streams,” said Ken Cook, president of the nonprofit Environmental Working Group. “It took too long,” adding, “The findings are fairly consistent with what we know about the larger river system.”

The data was collected from 2000 to 2004. The agency said it plans on expanding the study to Hawaii and Alaska in future studies.