The Colorado River is a critical resource for the western U.S. But a megadrought, one significantly exacerbated by climate change, is jeopardizing the river's future and threatening to upend how its water is used and longstanding agreements between states. Miles O'Brien reports as part of our coverage on how climate change is creating a "Tipping Point" for the U.S. and around the world. PBS NewsHour is supported by - https://www.pbs.org/newshour/about/funders