More than half of the country’s rivers and streams are in poor biological health, unable to support healthy populations of aquatic insects and other creatures, according to a nationwide survey released Tuesday.
The Environmental Protection Agency sampled nearly 2,000 locations in 2008 and 2009 — from rivers as large as the Mississippi River to streams small enough for wading. The study found more than 55 percent of them in poor condition, 23 percent in fair shape, and 21 percent in good biological health.
The most widespread problem was high levels of nutrient pollution, caused by phosphorus and nitrogen washing into rivers and streams from farms, cities and sewers. High levels of phosphorus — a common ingredient in detergents and fertilizers — were found in 40 percent of rivers and streams.
Another problem detected was development. Land clearing and building along waterways increases erosion and flooding and allows more pollutants to enter waters.
“This new science shows that America’s streams and rivers are under significant pressure,” said Nancy Stoner, acting assistant administrator of the EPA’s water office. “We must continue to invest in protecting and restoring our nation’s streams and rivers, as they are vital sources of our drinking water, provide many recreational opportunities and play a critical role in the economy.”
Conditions are worse in the East, the report found. More than 70 percent of streams and rivers from the Texas coast to the New Jersey coast are in poor shape. Streams and rivers are healthiest in Western mountain areas, where only 26 percent were classified as in poor condition.
The EPA also found some potential risks for human health.
In 9 percent of rivers and streams, bacteria exceeded thresholds protective of human health. And mercury, which is toxic, was found in fish tissue along 13,000 miles of streams at levels exceeding health-based standards. Mercury occurs naturally but also can enter the environment from coal-burning power plants and from burning hazardous wastes.
The Obama administration finalized regulations to control mercury pollution from coal-burning power plants for the first time in late 2011.