Cappaert v. United States
426 U.S. 128 · 1976 · Supreme Court of the United States
Holding
When the United States reserved Devil's Hole as part of a national monument in 1952, it acquired by implication reserved rights in unappropriated appurtenant water sufficient to maintain the underground pool's level and preserve its scientific value (the desert pupfish's habitat), but only the amount necessary for that purpose. The doctrine lets the United States protect its reserved water from later diversions whether the diversion takes surface water or groundwater.
"it reserves water rights sufficient to accomplish the purposes of the reservation" — Syllabus, Cappaert v. United States, 426 U.S. 128 (1976)
Why it matters for settlements
Confirmed that reserved rights are capped at the minimum necessary to fulfill the reservation's purpose while reaching hydrologically connected water, a bridge later cited in tribal groundwater litigation.
Sources
- CourtListener search API (citation, date, court, canonical URL) (courtlistener.com, retrieved 2026-09-01)
- Justia (syllabus and opinion text; cross-check) (supreme.justia.com, retrieved 2026-09-01)
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