Approximately 55% of the nation's rivers and streams are in poor condition for aquatic life, an Environmental Protection Agency survey released Tuesday found, citing pressure from nitrogen or phosphorus runoff, rising bacteria levels or diminishing surrounding vegetation.
"The health of our Nation's rivers, lakes, bays and coastal waters depends on the vast network of streams where they begin, and this new science shows that America's streams and rivers are under significant pressure," said Nancy Stoner, Office of Water acting assistant administrator
The most prevalent contaminants EPA found through data collected from approximately 2,000 sites across the country, are nitrogen and phosphorus – showing up in excessive levels in 27% and 40% of streams and rivers, respectively.
Data for the survey was collected between 2008-2009 by states and tribes and analyzed by EPA, state and university scientists.
The assessment also looked at how stressors would impact overall health over time. EPA says too much nitrogen and phosphorus in the water can harm water quality by promoting algae growth. The algae limits food resources and habitats, and decreases the oxygen that fish and other aquatic life need.
Higher mercury levels also appeared as a concern. EPA says 13,000 miles of rivers have fish with mercury levels that might be unsafe for consumption. Eating fish with high mercury levels may harm an unborn baby or young child's developing nervous system.
High bacteria levels were found in 9% of stream and river miles, creating concern for recreational use.
Health vegetative cover, which improves resistance to flooding, erosion and pollution, was also examined in the latest assessment. EPA found 24% of rivers and streams were rated "poor" because of limited or decreased vegetative cover. The vegetation also helps to maintain water temperatures and slow river flows.
EPA says it will use the data to make decisions regarding water body health. The survey will also help develop improvements to monitoring these rivers and streams across jurisdictional boundaries and enhance the ability of states and tribes to assess and manage water quality.
"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," Stoner said.
Click here for a look at the full survey.