According to the group American Rivers, the Colorado river is the most endangered river in the United States. Outdated water policies and climate change seem to be the main causes.
"We’re in our 12th or 13th year of prolonged drought in the basin; we’ve had below-average precipitation most years, and that is compounded upon itself, year to year. Reservoirs like Lake Mead and Lake Powell are at about 50 percent or slightly less capacity," said Matt Niemerski, director of American Rivers.