Colorado River water supports about 40 million people and millions of acres of farmland in the U.S. and Mexico.
In 1991, federal officials classified the razorback sucker as an endangered species.
The long-waited announcement comes as the river's two largest reservoirs, Lake Mead and Lake Powell, have been drained to alarmingly low levels.
Arizona water managers have been leading a series of biweekly meetings since July to work out details of the proposed drought-contingency plan.
An all-female cast reenacts the exploits of explorer John Wesley Powell's 1869 expedition along the Colorado River.
Drought has severely affected reservoir levels in Colorado and water supply is well below normal in almost all of the state’s major basins.
A species of trout thought to be extinct was found and rescued.
“If storage in Lake Powell cannot rebound in an era where the Upper Basin consumes less than two-thirds of its legal apportionment, then the crisis is already real.”
The chances of a shortfall in Lake Mead, the Colorado River’s biggest reservoir, are now 57 percent, up from the 52 percent projected in May.
Colorado Parks and Wildlife officials have fishing restrictions in nearly a half dozen rivers across the state.