Arizona v. California
Headline: Federal decree establishes specific mainstream water-use rights and priority dates for Arizona, California, and Nevada, formalizing statewide allocations and giving Indian reservations protected priority when water is scarce.
Holding:
- Fixes exact annual water quantities and priority dates for major users in three states.
- Gives certain Indian reservations first priority when mainstream water is insufficient.
- Appoints a Special Master to manage further proceedings and filings.
Summary
Background
The United States, the State of Arizona, several California water districts and cities, and the State of Nevada agreed to a supplemental decree that spells out each party’s current rights to use mainstream river water and the dates those rights began. The Court granted the joint motion to enter that supplemental decree and listed quantities, priority dates, and conditions for those present perfected rights. The decree also sets unit diversion amounts for five Indian reservations.
Reasoning
The main question was whether to accept and enter the agreed supplemental decree fixing present water rights and priorities. The Court approved the list as presented, with conditions: the list measures amounts by diversions or by the water needed to irrigate specified acres, does not change other parts of the original decree, and limits use to beneficial purposes. The Court also directed that, if water is insufficient, certain Indian reservations must be fully satisfied first and appointed a Special Master to manage further proceedings. A motion by the Fort Mojave Tribe to intervene to oppose the decree was denied in part.
Real world impact
The order fixes who may use how much river water and when those rights began, affecting irrigation districts, cities, federal projects, and reservations. In shortages, the listed reservations receive priority protection. The Special Master and the Secretary of the Interior will carry out future adjustments and handle disputes, and boundary or settlement changes can lead to later quantity adjustments.
Dissents or concurrances
Justice Marshall did not participate in the case; other intervention motions were referred to the Special Master for further handling.
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