Mexico and the U.S. states of Arizona and Nevada face a better-than-even possibility of getting less water from the Colorado River in 2020 because of a persistent drought, water managers said Wednesday. The U.S. Bureau of Reclamation, which manages the river, released projections showing a 52 percent chance the river’s biggest reservoir, Lake Mead in Arizona and Nevada, will fall low enough in 2020 to trigger cutbacks under agreements governing the system.