Veteran actor/director Robert Redford worries a drought that is set to last into the next century will kill off the Colorado River that flows through the U.S. Southwest. Environmentalist Redford, who narrates new IMAX documentary Grand Canyon Adventure: River At Risk 3D, is concerned about water conservation as the Colorado provides water to 27 million people living in the region. He says, "(The river is) endangered now on a number of fronts. Its volume is shrinking because of a mega-drought cycle that's now facing the Southwest, and some scientists predict that it could last into the next century."