The Colorado River flows from the western foothills of the Colorado Rocky Mountains through Utah, Arizona, Nevada, California and Mexico before debauching in the Gulf of California. Or at least it used to. As one of the major river systems in the Western U.S., the Colorado provides water to nearly 30 million people. Waters from the Colorado have turned the desert Imperial Valley of California into the lettuce growing capitol of the U.S. Hydrologists separate its drainage basin into the Upper Colorado and Lower Colorado River basins.
Udall, B., Colorado State Univ., 2017, Climate change is shrinking the Colorado River. https://source.colostate.edu/climate-change-shrinking-colorado-river/