(CNN) -- A U.S. conservation group released a list Wednesday of what it says are America's 10 most endangered rivers, which face man-made threats from gas drilling and new dams to outdated flood management.
The list and accompanying report from American Rivers highlights the threats facing each waterway and urges the public to act to protect them.
Topping the list is the Upper Delaware River, which divides northeast Pennsylvania from southeast New York state and provides drinking water for 17 million people across both states. Natural gas drilling in the area threatens the river as a clean water source, the group said.
Gas drilling is also threatening the Monongahela River in southwestern Pennsylvania and northern West Virginia, the group said. The river, which is ninth on the list, provides drinking water for hundreds of thousands of people and is home to some of the East Coast's best fishing, whitewater boating, and wildlife, the group said.
Both the Upper Delaware and the Monongahela sit on an area called the Marcellus Shale, which lies beneath large parts of Pennsylvania, New York, and West Virginia at a depth of 5-8,000 feet, according to the Pennsylvania Department of Environmental Protection.
The shale is believed to hold trillions of cubic feet of natural gas. It has long been considered too expensive to access, according to the department, but recent technological advances and rising natural gas prices have rekindled an interest in drilling beneath the Marcellus Shale.
American Rivers says the natural gas extraction involves injecting chemicals into the ground, creating untreatable toxic wastewater. It urged the Delaware River Basin Commission not to issue new permits for gas drilling in the area until there can be a thorough study of its impacts, and it urged Congress to pass the Fracturing Responsibility and Awareness of Chemicals Act of 2009.
Along the Monongahela, American Rivers urged the Ohio River Valley Water Sanitation Commission and state authorities to prohibit pollution associated with the drilling.
The Pennsylvania Department of Environmental Protection says the wastewater from the drilling is treatable, and that disruption of water quality is "often rare and generally temporary."
Outdated water and flood management threaten the second river on the list, the Sacramento-San Joaquin River Delta. It supplies drinking water for 25 million people, irrigates important agricultural land, and provides critical habitat for salmon and migratory birds, the group said.
The water and flood management have decimated the ecosystem and left Californians more vulnerable to droughts and floods, American Rivers said. It urged Governor Arnold Schwarzenegger to advance floodplain restoration in the last months of his term.
The proposed construction of new dams is a risk to the Little River in North Carolina and the Teton River in Idaho, the group said. Both are home to abundant wildlife and offer recreation, and the Little River also provides drinking water and irrigation, American Rivers said.
A proposed water supply dam on the Little River would be too costly and harm the river's health, the group said.
The proposed dam on the Teton is a rebuilding of one that burst 35 years ago, causing deaths and flooding across farmland. The group says the new one would be unsafe and unnecessary, and it urged authorities to focus on more cost-effective and reliable water supply solutions.
In Colorado, more than a century of water diversions have damaged the Upper Colorado River, which is home to prized trout fisheries and draws anglers and paddlers from across the country.
"If two new major proposed diversion projects advance without the right provisions, the river could become a shadow of its former self," American Rivers said. "Conversely, if the projects move forward with appropriate foresight and consideration for the long-term protection of the river's health, it could usher in a new era of stewardship and recovery for the Upper Colorado."
Elsewhere, mining is a threat to nearby rivers, the group said.
Mountaintop removal coal mining, in which mountaintops are flattened, is harming the Gauley River in West Virginia, which is internationally famous for its white water, American Rivers said. The mining buries streams under debris and pollutes the water, it said, and it urged the U.S. Environmental Protection Agency to stop permitting harmful mining activity.
Proposals for suction dredge mining -- a gold-mining technique -- will harm southern Oregon's Chetco River, which has abundant salmon and trout, the group said.
Suction dredge mining involves engines that suck up sediment from stream bottoms to sort for gold, then spit the debris back into the river bed, according to California State Sen. Pat Wiggins, who supported legislation to ban it in her state. Fish eggs and larvae are killed when sucked through the machines and the streambeds are altered, leaving unstable spawning beds for salmon, she said.
The Cedar River in Iowa faces a threat from outdated flood management and poor watershed planning, which is causing pollution and increasing flood risks, the group said.
Alabama's Coosa River was damaged in the middle of the past century by the construction of seven hydropower dams, which turned the river into a series of reservoirs and caused the extinction of more than 35 species, conservation groups say. It is still home to a variety of rare or unique fish, snails, and mussels.
American Rivers urged the U.S. Fish and Wildlife Service to insist on wildlife protections in granting licenses for the continued operation of the Coosa dams.