Two members of Arizona’s congressional delegation introduced legislation Tuesday on a plan to address a shrinking supply of water from a river that serves 40 million people in the U.S. West. Republican Sen. Martha McSally and Democratic Rep. Raul Grijalva vowed to move identical bills quickly through the chambers. Bipartisan lawmakers from Colorado River basin states signed on as co-sponsors. Arizona, California and Nevada in the lower basin and Colorado, New Mexico, Utah and Wyoming in the river’s upper basin spent years crafting drought contingency plans. They aim to keep two key Colorado River reservoirs from falling so low that they cannot deliver water or produce hydropower.