WINDOW ROCK, Ariz. (AP) — The Navajo Nation Council has signed off on a proposed water rights settlement that carries a price tag larger than any such agreement enacted by Congress would ensure water for two other Native American tribes in a state that has been forced to cut back on water use.

The Navajo Nation has one of the largest single outstanding claims in the Colorado River basin. Delegates acknowledged the gravity of their vote Thursday, with many noting that securing water deliveries to tribal communities has been an effort that has spanned generations.

“Thank you for helping make history today,” Navajo Council Speaker Crystalyne Curley told her fellow delegates as they stood and clapped after casting a unanimous vote.

The Hopi tribe approved the settlement earlier this week, and the San Juan Southern Paiute Council was expected to take up the measure during a meeting Thursday. Congress will have the final say.

Congress has enacted nearly three dozen tribal water rights settlements across the U.S. over the last four decades and federal negotiation teams are working on another 22 agreements involving dozens of tribes. In this case, the Navajo, Hopi and San Juan Southern Paiute tribes are seeking more than $5 billion as part of their settlement.

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About $1.75 billion of that would fund a pipeline from Lake Powell, one of the two largest reservoirs in the Colorado River system, on the Arizona-Utah border. The settlement would require the U.S. Bureau of Reclamation to complete the project by the end of 2040.

From there, water would be delivered to dozens of tribal communities in remote areas.

Nearly a third of homes in the Navajo Nation — spanning 27,000 square miles (70,000 square kilometers) of Arizona, New Mexico and Utah — don’t have running water. Many homes on Hopi lands are similarly situated.

A century ago, tribes were left out of a landmark 1922 agreement that divided the Colorado River basin water among seven Western states. Now, the tribes are seeking water from a mix of sources: the Colorado River, the Little Colorado River, aquifers and washes on tribal lands in northeastern Arizona.

The latest settlement talks were driven in part by worsening impacts from climate change and demands on the river like those that have allowed Phoenix, Las Vegas and other desert cities to thrive. The Navajo, Hopi and San Juan Southern Paiute tribes are hoping to close the deal quickly under a Democratic administration in Arizona and with Joe Biden as president.

Without a settlement, the tribes would be at the mercy of courts. Already, the U.S. Supreme Court has ruled that the federal government is not bound by treaties with the Navajo Nation to secure water for the tribe. Navajo has the largest land base of any of the 574 federally recognized tribes and is second in population with more than 400,000 citizens.

A separate case that has played out over decades in Arizona over the Little Colorado River basin likely will result in far less water than the Navajo Nation says it needs because the tribe has to prove it has historically used the water. That’s hard to do when the tribe hasn’t had access to much of it, Navajo Attorney General Ethel Branch has said.

Arizona — situated in the Colorado River’s Lower Basin with California, Nevada and Mexico — is unique in that it also has an allocation in the Upper Basin. The state would get certainty in the amount of water available as it’s forced to cut back as the overall supply diminishes.

Navajo and Hopi, like other Arizona tribes, could be part of that solution if they secure the right to lease water within the state that could be delivered through a canal system that already serves metropolitan Tucson and Phoenix.

Arizona water officials have said the leasing authority is a key component of the settlement.