From its headwaters in the Rockies, the Colorado River meanders 1,400 miles through five states and into Mexico, nourishing 40 million people and irrigating 5.5 million acres of farmland along the way. Despite decades of subsequent development, the water rights first established by the Colorado River Compact in 1922 remain essentially unchanged today. The agreement allocates 15 million acre-feet each year (picture an acre of land covered with a foot-high layer of water) among the seven Colorado River Basin states: Wyoming, Utah, Colorado, New Mexico, Nevada, Arizona, and California. The compact also acknowledged Mexico’s right to water, and in 1944, the nation was guaranteed 1.5 million acre-feet, bringing the total to 16.5 million. For many years, states rarely took all they were owed; currently, the river can’t come close to meeting demand.