In the United States, 40 million people in seven states depend on water provided by the Colorado River. After 20 years of drought, the situation is dire and the river is at risk of becoming a “deadpool,” a condition in which there is not enough water to pass through the dams. The states were supposed to come up with a deal to cut their usage by Tuesday. Now, the federal government may have to step in and make a difficult decision. Guest: Christopher Flavelle, a climate reporter for The New York Times.