IN EARLY NOVEMBER, the U.S. Supreme Court agreed to hear a case brought by the Navajo Nation that could have far-reaching impacts on tribal water rights in the Colorado River Basin. In its suit, the Navajo Nation argues that the Department of the Interior has a responsibility, grounded in treaty law, to protect its future access to water from the Colorado River. Several states and water districts have filed petitions opposing the Navajo Nation, stating that the river is “already fully allocated.” The case highlights the growing tension in the region: Tribes are still working to ensure their water rights are fully recognized and accessible, while states face increasing water cuts amid a two-decade-long drought.
The Colorado River used to provide roughly 15 million acre-feet of water a year. (For scale, one acre-foot of water can supply one to three households annually.) A century ago, states reached an agreement to divide that water among themselves. In recent decades, the river has
