Two environmental groups are warning of danger to rivers both in the United States and elsewhere in the world from toxic chemicals and development.
The list published by the conservation group American Rivers singles out those waterways facing severe toxic cleanup by the U.S. Environmental Protection Agency and local governments.
A representative of American Rivers, John Senn, says 10 U.S. rivers need major cleanup efforts.
"Endangered rivers aren't America's worst or polluted rivers, but they are all in danger of taking a turn for the worse," he said. "The endangered label is both about problems and solutions. It's a cry for help, not an admission of defeat."
Topping the conservation group's endangered list is the Colorado River, which flows through several Western U.S. states.
American Rivers' John Senn says the river is not yet the most polluted river in the country, but it may soon be if the current problems are left unchecked.
"There are threats to drinking water on the Colorado River because of a chemical used in rocket fuel," Mr. Senn said. "Gallons upon gallons of that [chemical] seep into the Colorado River every day. Another threat is an 11 million ton pile of radioactive waste, which is sitting on the river's banks in Utah."
Reacting to the report, Janet Napolitano, the governor of Arizona, through which the river flows, said she would coordinate with officials from other states along the Colorado river and with Federal officials to protect the waterway. She noted that while the Colorado water, which 30 million people rely on, is currently safe to use, action must be taken to ensure its future safety.
Another river on the endangered is the Mississippi that flows through 10 states. It is threatened by river traffic, pollution and other causes. In the northeastern United States, the Housatonic River, which flows from Massachusetts through Connecticut to New York's Long Island Sound, is also on the list. It has one of the highest concentration of PCB's, a now-banned synthetic chemical that has been linked to cancer in the U.S.
The General Electric Company, which manufactured the chemical and the Environmental Protection Agency have removed contaminated sediment from the heavily polluted waters closest to its plant. But officials have to decide whether to clean up the remaining 237 kilometers of river.
EPA officials working on the Housatonic cleanup have agreed that the next few years will determine the river's long-term environmental recovery.
Outside the United States, river conservation groups are more focused on the effects of massive infrastructure projects on waterways.
Patrick McCully is campaigns director of the International Rivers Network, a California-based group that monitors dam projects around the world. He says dams are the greatest threat to waterways in Asia and Africa.
"There are a lot of rivers around the world that are in a really bad state and threatened to get into a worse state because of the development plans going on," he said. "The big difference is that in the U.S., big dam building has stopped. Around the rest of the world, there are still big dams getting built."
Mr. McCully says dam projects like the estimated $200 billion river interlinking project in India, which will connect all the major rivers in the country, will displace millions of people who live along the waterways, and kill the rivers' ecosystems.
Dams such as the controversial Three Gorges in China are built for irrigation purposes, domestic water supply, flood control, and hydroelectric power plants.
But in an unexpected move, Chinese Prime Minister Wen Jiabao halted plans for another massive dam system in western China. He then called for a review of the environmental impact on one of the country's last unspoiled places.