Arizona v. California
373 U.S. 546 · 1963 · Supreme Court of the United States
Holding
In the original-jurisdiction apportionment of the lower Colorado River, the Court sustained the Special Master's findings that the United States reserved water for five Indian reservations when it created them, in an amount sufficient to irrigate all the practicably irrigable acreage on the reservations, covering future as well as present needs, with priority dating from each reservation's creation.
"enough water was reserved to irrigate all the practicably irrigable acreage" — Syllabus, Arizona v. California, 373 U.S. 546 (1963)
Why it matters for settlements
Established practicably irrigable acreage (PIA) as the quantification standard for tribal reserved water rights and confirmed that reservations created by Executive Order also carry reserved water.
Sources
- CourtListener search API (citation, date, court, canonical URL) (courtlistener.com, retrieved 2026-09-01)
- Justia (syllabus incl. PIA holding; cross-check) (supreme.justia.com, retrieved 2026-09-01)
Related: doctrine overview · all cases · settlements table