Nearly a third of the Navajo households do not have running water and must rely on water that is trucked in. The Navajo Nation blames the U.S. government for having breached its duty of trust that came with an 1868 treaty that established their reservation in what is now northeast Arizona and smaller portions of southeastern Utah and northeastern New Mexico.

That treaty “promised both land and water sufficient for the Navajos to return to a permanent home in their ancestral territory,” attorneys for the Navajo Nation told the court. “Broken promises. The Nation is still waiting for the water it needs.”

The case comes before the justices during an era of drought in the West and 100 years after execution of the Colorado River Compact that divided water among seven states including California, Arizona and Nevada.

At issue now is whether the Navajo Nation can press ahead with a lawsuit that seeks a federal plan to supply its residents’ unmet need for water.

The Navajo Nation won a preliminary victory in the 9th Circuit Court of Appeals in 2021, which said it had a claim for breach of trust, noting that the 1868 treaty referred to agriculture.

“The Nation’s right to farm reservation lands … gives rise to an implied right to the water necessary to do so,” the appeals court said. However, it stopped short of deciding whether this included “rights to the mainstream of the Colorado River or any other specific water sources.”

But in the fall, the Supreme Court agreed to hear appeals from both the Interior Department and Arizona that seek to toss out the 9th Circuit’s decision.

U.S. Solicitor Gen. Elizabeth B. Prelogar argued the 1868 treaty said nothing about water and established no specific duties for the government related to water. Moreover, the Navajo Nation has been given water rights from two tributaries of the Colorado River, including San Juan River in Utah, she said.

Lawyers for Arizona, joined by the Metropolitan Water District of Southern California, said the high court’s decrees have allocated the waters from the lower Colorado River, and it is too late for lawsuits that seek new rights to the same water.

The cases are Arizona vs. Navajo Nation and Department of Interior vs. Navajo Nation.