Arizona v. California

Background

This case settles who may use water from the mainstream Colorado River and some of its tributaries. The parties include the United States, the states of Arizona, California, Nevada, and New Mexico, irrigation districts, cities, counties, and several Native American reservations. The decree defines key terms, recognizes “present perfected rights” as of June 25, 1929, and ties deliveries to contracts and to operations of federally controlled dams and reservoirs.

Reasoning

The Court addressed how mainstream water below Lee Ferry must be released and to whom. It ordered that federal releases follow a priority for river regulation, irrigation and domestic uses (including recognized prior rights), then power. The decree fixes an annual baseline of 7,500,000 acre-feet apportioned 2,800,000 to Arizona, 4,400,000 to California, and 300,000 to Nevada, spells out how surplus or shortages are handled, and lists specific annual amounts for named Indian reservations and federal areas. It requires valid contracts for deliveries and gives the Secretary of the Interior the job of determining available water and administering apportionments.

Real world impact

The decree binds the United States, the named states, and water users to these allocations and limits. New Mexico faces numerical limits on diversions from specific streams and must keep detailed records. The United States must keep annual, public records of releases, diversions, deliveries to Mexico, and consumptive uses. The Court retained jurisdiction to amend or supplement the decree in the future.

Dissents or concurrances

Mr. Justice Douglas dissented, and Justices Harlan and Stewart registered partial dissents; the Chief Justice did not participate. Their disagreements are noted but do not change the decree.