Water rights can get ugly. As Arizona prepares to sue for Colorado River water rights, LASN examined at the history of litigation and water rights to the river.

In 1952, the case, Arizona v. California began with Arizona filing of an action in the Supreme Court by Arizona seeking a division of the water within the Colorado River. The federal government intervened to protect their rights, and five Indian reservations, Nevada, Utah, and New Mexico, also stepped in. From there, the Court appointed a special master who conducted proceedings and recommended divisions.

 
Then in a 1963 decision, the Supreme Court adopted the recommendations and issued the division in '64, which formed the Colorado River Compact between the Upper and Lower Basin states. However, it did not provide a subdivision between the Lower Basin States - Arizona, Nevada, and California. The Court concluded that the Boulder Canyon Project Act authorized the construction of the All-American Canal and other Colorado River diversions.

The Court also determined that the U.S. had reserved water rights for five Indian reservations by the Court's earlier decision in Winters v. United States. The 1908 case held that the U.S. creation of an Indian reservation reserved sufficient water to irrigate. The Court adopted the Master's findings regarding the amounts of practicably irrigable lands on the various reservations, the corresponding amounts of water that the Tribes were entitled to withdraw from the mainstream of the River, and the priority dates of those rights. The Court, however, did not resolve disputes regarding the boundaries of the Fort Mojave and Colorado River Indian Reservations. These disputes led to additional litigation.

Then, in 2023, the Court ruled in a split vote regarding the Navajo Nation and the federal government. The states that drew from the river urged the court to rule against the tribe because it would undermine existing agreements. As the federal court originally dismissed the lawsuit, an appeals court allowed it to move forward. The court ruled in a 5-4 decision that the 1868 Navajo Treaty did not include that the federal government has an affirmative duty to secure water access for the Navajo Nation.

Considering all of this, Arizona is preparing for another possible legal battle as it negotiates a new multistate agreement. A new agreement could ease the burden on Arizona, users especially those dependent on the Central Arizona Project - a 336-mile diversion canal system. Gov. Katie Hobbs proposed allocating $3 million to the Arizona Department of Water Resources for future litigation over the agreement that additional cuts could be needed.

In 2007, the basin states agreed to guidelines that dictate how cuts are allocated during shortages. However, these guidelines expire at the end of next year. The 1922 compact dictates how much water each state is entitled to, but levels have consistently fallen short. So, in the meantime, Arizona is preparing for less water.