Arizona v. California
The Supreme Court entered a consolidated decree in its decades-long original-jurisdiction case over the Colorado River, approving settlements of water-rights claims for the Fort Yuma Indian Reservation and folding earlier decrees dating back to 1964 into one master document.
The decree does not change existing water allocations among Arizona, California, and Nevada or with the affected tribes; it consolidates and updates the record so the rights and obligations of everyone involved can be found in a single place.
How it got here: This original-jurisdiction suit between states has run since 1953 through multiple Special Masters and decrees; the parties jointly asked the Court to approve settlements and enter one consolidated decree.
The Case in Depth
What happened
Since the 1950s, Arizona and California (along with Nevada, New Mexico, Utah, the United States, and several tribes) have litigated how much Colorado River water each may use. Over decades the Court entered a series of decrees fixing allocations among the states and reserving specific quantities for Indian reservations, national wildlife refuges, and other federal lands along the river.
The question before the Court
How should Colorado River water be divided among Arizona, California, Nevada, and Native American tribes along the river?
Why it matters
Farmers, cities, water districts, and Native American tribes across Arizona, California, and Nevada rely on precise, court-ordered shares of Colorado River water. This decree gives officials and water users one authoritative document listing exact quantities and priority dates, reducing confusion from having to cross-reference five separate decrees issued over more than 40 years.
What changes now
The consolidated decree is now the controlling reference for Colorado River water rights among Arizona, California, Nevada, and the affected tribes and federal lands. The Special Master, Frank McGarr, was formally discharged. The Court retains jurisdiction over the case and any party may still return to ask for further relief, amendments, or clarification of the decree's terms.
What this does not decide
The decree explicitly states it does not vacate or change the substantive rights fixed by the earlier decrees except where its text differs, does not resolve boundary disputes for certain reservations, and does not decide any issue about interpreting the Colorado River Compact or rights on other tributaries.
How the Court got there
The legal reasoning, step by step
- The Court had previously approved a series of decrees (1964, 1966, 1979, 1984, and 2000) fixing Colorado River water shares among Arizona, California, and Nevada and reserving specific quantities for named Indian reservations and federal lands.
- A Special Master submitted a report in 2005 recommending approval of a settlement resolving the long-pending federal reserved water rights claim for the Fort Yuma Indian Reservation.
- The states, relevant water districts, the United States, and the Quechan Tribe jointly asked the Court to approve that settlement and to combine all of the prior decrees into one consolidated document for ease of reference.
- The Court approved the settlement agreements and found that combining the substantive provisions of the earlier decrees into a single decree, without altering their underlying rights and obligations, served the goal of giving the parties one clear reference document.
- Consistent with that approval, the Court adopted detailed provisions defining key terms, setting the priority order for water releases, fixing state and tribal allocations, and preserving each party's existing rights except where the new decree's text expressly differs.