Conservation group American Rivers announced America's Most Endangered Rivers of 2015 today, placing the Colorado River in the Grand Canyon at the top of the list. “One of our country's most iconic stretches of river and an irreplaceable national treasure, the Colorado River in the Grand Canyon faces a battery of threats that could forever harm its health and unique experience that belongs to every American,” AR said in a statement.

One of these threats is the Grand Canyon Escalade project, a proposed tramway that would carry up to 10,000 visitors a day from a two million square foot development on the canyon rim to the confluence of the Colorado and Little Colorado rivers at the bottom of the canyon.

"This billion dollar scheme would be a travesty, destroying the very qualities that make the Grand Canyon such a spectacular life-changing experience, and an economic engine for the region," said American Rivers President Bob Irvin.

Other development concerns include existing and proposed uranium mining operations and a major expansion of the town of Tusayan just outside the borders of Grand Canyon National Park. If built, the proposed 2,200 new homes would mean a 1,000 percent expansion of the town’s current population. New groundwater extraction could deplete springs that feed ecologically sensitive areas and change the character of some of the Grand’s most iconic side canyons.

"The Grand Canyon is facing the biggest threats in a generation," Irvin said. "The Colorado River in the Grand Canyon is an irreplaceable national treasure that should be preserved for all of us, for all time. The Grand Canyon is not for sale."

–Read more about the Grand Canyon and other endangered rivers on American Rivers’ website and sign their petition to Secretary of Interior Sally Jewell: