Natural gas development, outdated flood management, and dams are the biggest threats to the 10 most endangered rivers in the U.S., according to the most recent national assessment by American Rivers, a Washington-based national advocacy group.

The 2010 edition of the report, America’s Most Endangered Rivers, found that two of the 10 most endangered rivers, the Upper Delaware and the Monongahela, are threatened by natural gas drilling in watersheds that both drain into New York and Pennsylvania.

American Rivers is most concerned with the energy development process of hydraulic fracturing, which is the use of water and chemicals, pumped under pressure into drilling shafts, to fracture rock and provide spaces through which natural gas flows to the well. It has been linked in seven states to contamination in aquifers, though the industry asserts that decades of experience with “hydrofracking,” as its commonly known, is safe.

The U.S. Environmental Protection Agency has launched a comprehensive analysis of hydrofracking that will update a report on the process it finished in 2004, when the agency said it was not a threat to drinking water.

“This is the first year we have put a river on the list for the hydraulic fracture process,” said Amy Kober, communications director for American Rivers. “I think we really need to take a hard look and make sure we have restrictions and safeguards in place on gas drilling so it can be done safely.”

In addition to man-made influences, increased floods, droughts and water pollution related to climate change have further complicated the health of rivers.

“These rivers are all at a crossroads, there is a major decisions hanging over them that will determine their fate.” Ms. Kober told Circle of Blue, “We want people to be weigh in and make a difference.”

The 2010 threatened rivers report is the 25th published by American Rivers. The principal threats identified by American Rivers have evolved in that time span from dams and logging in the 1980s, to urban and suburban development in the 1990s.

The report is the first to identify drilling practices as the primary risk to rivers, and is consistent with escalating environmental and human costs of satisfying the nation’s insatiable demand for fossil fuels.

“When a river is endangered the community that depends on that river is endangered,” said Kober.

Here’s a look at the top 10 most endangered rivers in the U.S.: (More)

This article is republished by permission of Circle of Blue, a news and science organization based in Traverse City, Mich. that covers the global freshwater crisis. Heather Rousseauis a reporter and photojournalist for Circle of Blue. Reach her at heather@circleofblue.org.