Arizona v. California
Headline: Court updates Colorado River water allocations for several Native American tribes, approves their intervention, and fixes annual diversion amounts and priority dates affecting reservation irrigation and water use.
Holding: The Court entered a second supplemental decree implementing its March 30, 1983 decision by allowing several tribes to intervene and by fixing specific annual diversion amounts, irrigated acres, and priority dates for their reservation water rights.
- Sets exact annual water amounts tribes can divert for reservation irrigation.
- Establishes priority dates that affect who gets water during shortages.
- Charges 2,026 acre-feet against Arizona for the Cocopah reservation.
Summary
Background
This order implements the Court’s March 30, 1983 decision about water rights for several Native American tribes. The Fort Mojave, Chemehuevi, Colorado River, Quechan, and Cocopah tribes were allowed to intervene. The Court amended earlier decrees from 1964 and 1979 to record specific annual water amounts, irrigated acreage, and priority dates for these reservations.
Reasoning
The Court’s action was procedural and remedial: it applied its prior ruling by changing numbered paragraphs in the earlier decrees. The decree records precise limits—measured either as diversions in acre-feet or as the consumptive use needed to irrigate specified acres—and assigns priority dates for each reservation’s right. It also approves the Special Master’s cost allocation, discharges the Special Master, and keeps the Court’s power to order further proceedings.
Real world impact
The decree determines how much mainstream Colorado River water each named reservation may divert each year and what acres those amounts support, which affects irrigation and related uses on reservations. It sets priority dates that influence who gets water first during shortages. The decree also charges a 2,026 acre-foot diversion right for the Cocopah against the State of Arizona with a 1974 priority, and it allows future adjustments if reservation boundaries are finally determined.
Dissents or concurrances
Justice Marshall took no part in considering or deciding this matter, as noted in the decree.
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