Arizona v. California

Background

This dispute arose from a long-running lawsuit between Arizona and California over rights to Colorado River water, joined by Nevada, New Mexico, Utah, the United States, and several Indian tribes and local water districts. The Court reviewed decades of proceedings and prior decrees (entered in 1964, 1966, 1979, 1984, and 2000) and received a Special Master’s report recommending approval of settlements, including the federal reserved water rights claim for the Fort Yuma Indian Reservation. The parties filed a joint motion asking the Court to enter a consolidated decree that gathers the substantive provisions into a single document.

Reasoning

The Court approved the final settlement agreements, granted the joint motion, entered the proposed consolidated decree, and discharged the Special Master. The decree consolidates earlier orders and implements the Fort Yuma settlement. It sets rules for how the United States must operate and release river water, enjoins parties from unauthorized diversions or uses, and requires the Secretary of the Interior to keep and make available detailed annual records of releases, diversions, deliveries, and consumptive uses.

Real world impact

Practically, the decree fixes how mainstream Colorado River water is apportioned among the lower-basin States and federal establishments. For example, it provides for an annual baseline of 7,500,000 acre-feet divided as 2,800,000 for Arizona, 4,400,000 for California, and 300,000 for Nevada, with rules for surplus and shortage. It confirms specific annual diversion or consumptive-use quantities for multiple Indian reservations and water projects, and it preserves prior rights and the Court’s continuing jurisdiction to modify the decree if needed.