long-term health remains in serious doubt. between 2000 and 2021 rising temperatures sucked more than 10 trillion gallons of water out of the colorado river basin and that trend is likely to get worse. cnn s lucy kafanov went to moab, utah. reporter: this man has spent much of his life on the colorado river. it s a remarkable, remarkable area of the world. reporter: as an avid adventurer and colorado river advocate, his mission in life is to protect it. this is one of the most important places in the nation and it s one of the places that we need to be really diligent about taking care of because it does contribute soo much to all of us. reporter: the colorado river is the lifeblood of this region, powering cities, watering farms and quenching the thirst of some 40 million people. it s a critical refuge for wildlife and a playground that s under threat.