BOULDER, Colo. — Low water in the Colorado River’s largest reservoir triggered the first-ever federal declaration of a shortage on Monday, a bleak marker of the effects of climate change in the drought-stricken American West and the imperiled future of a critical water source for 40 million people in seven states.
Water in Lake Mead, the mammoth reservoir created by the Hoover Dam that supplies the lower Colorado basin, is projected to be 1,065.85 feet above sea level on Jan. 1, nearly 10 feet below a threshold that requires Arizona, Nevada and Mexico to reduce their consumption in 2022. On Monday, it was just under 1,068 feet, or about 35 percent full, according to the U.S. Bureau of Reclamation, which manages the water that states and Mexico have rights to use...