Burley Garcia|The Supreme Court wrestles with questions over the Navajo Nation's water rights

On Monday,Burley Garcia the U.S. Supreme Court heard arguments in a case that could alter the already intense battle over water rights in the parched American Southwest.

For more than 20 years, the Navajo Nation has fought for access to water from the lower Colorado River, which flows directly alongside the reservation's northwestern border.

The Navajo Nation reservation stretches across 27,000 square miles in Arizona, Utah and New Mexico. Almost a third of the 170,000 people who live there do not have access to clean, reliable drinking water, the tribe says.

Thousands who live without running water must drive for miles to refill barrels and jugs to haul water home for drinking, cooking, bathing and cleaning. Others rely on unregulated wells.

But the issue of access to the Colorado River is extremely contentious.

A decades-long drought, exacerbated by climate change, has created the driest conditions that the American Southwest has seen in centuries. The region's water supply is dwindling as its population and agricultural output have boomed.

The river, which provides water for 40 million people across the entire Southwest, is already overtapped. The seven states that rely on the river have long been embroiled in litigation over the body of water. Recently, they have struggled to reach an agreement on how to cut back on their water use.

But the Navajo Nation says it has not been able to fully represent its own interests in disputes over water. Instead, they say they've been blocked in court by the U.S. federal government, which says it represents tribal interests in water disputes.

The tribe's claim stems from federal policies that forcibly relocated tribes and their citizens westward and onto reservations, including the Navajo Treaty of 1868, said Heather Tanana, a law professor at the University of Utah.

"When they established these reservations, that came with the promise that those lands would be permanent homelands for the tribe and their people," said Tanana, who is a citizen of Navajo Nation. "And I think everyone would agree you can't have a homeland of any kind without water."

Both the tribe and the U.S. government agree that Indian reservations, including the Navajo Nation, have a right to water.

Now, the Supreme Court must decide how far the federal government's responsibilities go in reserving that right.

"Is the federal government the trustee and the Navajo Nation the beneficiary, such that ordinary trust law principles can be applied?" said Gregory Ablavsky, who specializes in federal Indian law at Stanford Law School. Ordinarily, he explained, a beneficiary can sue a trustee for mismanaging the trust — in this case, water.

Sympathy for the tribe's position came from Justice Neil Gorsuch, a frequent supporter of Native rights who has often split from his fellow conservatives on cases involving Indian treaties.

"Could I bring a good breach-of-contract claim for someone who promised me a permanent home, the right to conduct agriculture and raise animals if it turns out it's the Sahara Desert?" Gorsuch asked during Monday's oral arguments. (No, the government's lawyer replied.)

The U.S. has argued that a broad ruling in favor of the Navajo Nation could force the federal government to conduct an assessment of the tribe's water needs and build water supply infrastructure. Those responsibilities belong to the tribe, the government says.

"Just as the 1868 treaty didn't impose on the United States a duty to build roads or bridges, or to harvest timber, or to mine coal, the 1868 treaty didn't impose on the United States a duty to construct pipelines, pumps or wells to deliver water," said Frederick Liu, an assistant to the solicitor general, addressing the court.

Several of the court's conservatives, including Justices Samuel Alito and Brett Kavanaugh, appeared sensitive to that concern during Monday's hearing, which prompted assurances from Shay Dvoretzky, the attorney arguing on behalf of the Navajo Nation.

"The government hypothesizes a parade of horribles where the government would have to be building pipelines across miles and miles and miles of territory," Dvoretzky said. "We're not talking about anything like that."

States that rely on the Colorado River — including Arizona, California and Nevada — also oppose the tribe's efforts, saying that diverting water to the reservation would come at the expense of their states' populations and economies.

A favorable ruling would not immediately solve the tribe's water access issues, experts said. But it would allow the tribe's legal efforts around the Colorado River and other waterways to move forward.

"There isn't enough water. But that doesn't mean that the Navajo Nation does not have valid rights that should be enforced, that they should have the ability to develop their water and then play on the same level with every other stakeholder in the basin," said Tanana of the University of Utah.