By Jim Malewitz

More than half of the nation’s thousands of miles of rivers and streams are plagued by poor water quality, including harmful nutrient pollution and mercury, according to the U.S. Environmental Protection Agency.

That was the key finding of the agency’s first comprehensive examination of the health of U.S. waters, made public Tuesday.

“This new science shows that America’s streams and rivers are under significant pressure,” said Nancy Stoner, assistant administrator in the Office of Water. The findings are troubling, she said, considering the waterways’ vital role in providing drinking water, recreation and fueling the economy.

Fifty-five percent of these waters were considered to be in “poor” condition for aquatic life, while just 21 percent of the waters were considered “good.” The results were based on samples collected randomly from nearly 2,000 rivers during the summers of 2008 and 2009, the agency said.

Among the findings:

  • More than a quarter of rivers and streams registered high nitrogen levels and 40 percent had too much phosphorous. Such nutrient pollution, which typically runs off of farmland, sparks algae growth, eroding food supplies and depriving aquatic species of oxygen.
  • More than a quarter of rivers and streams are particularly prone to flooding, pollution and erosion because of a dearth of vegetation cover.
  • Nine percent of waters tested positive for high bacteria levels, making them not fit for swimming.
  • Fish in more than 13,000 of miles of water carried high levels of mercury, a toxic element particularly harmful to children and fetuses.
Conditions were typically better in the western U.S. than in the east, particularly across the mountain regions, where 26 percent of waters was in “poor” condition and 42 percent was “good.” Worst off was the Coastal Plains region, stretching from Eastern Texas to Florida and along much of the Atlantic coast. There, 71 percent of these waters was deemed “poor.”

The survey comes as several states are looking to address water pollution. States along the Mississippi River, for instance, are hashing out plans to cut down on nutrient pollution that has long choked the Gulf of Mexico.