A vital reservoir on the Colorado River will be able to meet the demands of Mexico and the U.S. Southwest for the next 13 months, but a looming shortage could trigger cutbacks as soon as the end of 2019, officials said Wednesday. A forecast from the U.S. Bureau of Reclamation echoes previous warnings that a nearly 20-year trend toward a drier regional climate coupled with rising demand could drain so much water from the Lake Mead reservoir that cutbacks would be mandatory.