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 Interior has a responsibility, grounded in treaty law, to protect future access to water from the Colorado River. Several states and water districts have filed petitions opposing the tribe, stating that the river is “already fully allocated.”

The case highlights a growing tension in the region: As water levels fall and states face cuts amid a two-decade-long megadrought, tribes are working to ensure their water rights are fully recognized and accessible.

On average, 15 million acre-feet of water used to flow through the Colorado River every year. For scale, one acre-foot of water could supply one to three households annually. A century ago, states reached an agreement to divide that water among themselves. But in recent decades, the river has supplied closer to 12 million acre-feet. Scientists say water managers in the basin need to plan for closer to 9 million acre-feet per year, a 40 percent decrease in a water source that supports 40 million people, due to climate change and aridification.

No states have made plans to accommodate this drop. Meanwhile, tribal nations are legally entitled to between 3.2 and 3.8 million acre-feet of ground and surface water from the Colorado River system.

There are 30 federally recognized tribes in the river’s basin, and 12 of them, including Navajo Nation, still have at least some “unresolved” rights, meaning the extent of their rightful claims to water have yet to be agreed upon.

Ultimately, Indigenous nations in the Colorado River Basin could be serious power brokers in crucial water negotiations to come — but they face historical, legal and practical obstacles. The Navajo Nation, for example, has rights to almost 700,000 acre-feet of water annually across New Mexico and Utah, along with unresolved claims in Arizona. But, because of a lack of infrastructure, up to 40 percent of Navajo households don’t have running water. For the Navajo Nation and other tribes with allocations in the basin, building and improving infrastructure means providing citizens with access to a fundamental human right: water.

Read the full article about Indigenous water rights by Jessie Blaeser, Joseph Lee and Anna V. Smith at Grist.