Federal Reserved Water Rights and Their Priority

Almost everything in western water law rewards action: divert, apply, record, maintain. Reserved rights reward none of it. They arise by implication from an act of Congress or an executive order setting land aside, they carry the priority of that act, and they survive indefinitely without a headgate, a permit or a single acre irrigated. In basins with an old federal reservation, they are the senior claim on the stream.

The implication, and what it covers

The doctrine holds that when the United States withdraws land from the public domain and reserves it for a federal purpose, it reserves by implication so much of the then-unappropriated water as is necessary to accomplish that purpose. Congress need not say so. The reservation of the land carries the water because the purpose would otherwise fail.

The Supreme Court extended the doctrine to groundwater where surface water alone cannot serve the purpose, holding that the United States could restrain pumping that lowered the level of a pool the reservation was created to protect. That extension matters increasingly, because most modern conflicts with reserved rights arise from wells rather than from diversions, and it links the doctrine to conjunctive administration of connected supplies.

A date without a diversion

Priority runs from the date of the reservation. A forest reserved long before a valley was settled outranks every farm below it, whether or not the United States has ever taken a drop. For tribal reservations the date is the establishment of the reservation, and for rights grounded in aboriginal use, such as fishing rights confirmed by treaty, courts have recognized a priority described as time immemorial.

Because the right does not depend on use, it is not subject to abandonment or statutory forfeiture. A century of nonuse extinguishes nothing. That is the feature that makes unquantified reserved claims so destabilizing: a basin can be fully appropriated and administered for generations under ordinary priority rules and still contain a senior claim that has never been exercised.

How much water the purpose requires

Quantification differs by reservation type, and the standards are not uniform.

The practicably irrigable acreage standard, developed for a large interstate case, asks how much land on the reservation could be irrigated with existing technology at a cost the project would justify, and awards the water necessary to irrigate it. The standard has been criticized for measuring a tribal homeland by an agricultural yardstick, and several settlements instead quantify a total volume the tribe may use for any purpose.

Two limits on the doctrine are worth stating plainly. A reserved right attaches only to water unappropriated at the moment of the reservation, so it never displaces an older appropriation. And the United States acquires no reserved right merely by owning land or by managing it; a mere federal proprietary interest, without a withdrawal for a stated purpose, produces nothing. Water for purposes outside the reservation's core must be obtained under state law in the ordinary way, which is why federal agencies file permit applications alongside private applicants.

Forum, settlement and the practical outcome

The McCarran Amendment consents to joinder of the United States in any suit for the adjudication or administration of rights to a river system, provided the proceeding is comprehensive. Federal courts ordinarily step aside in favor of a pending state proceeding, and state courts may adjudicate tribal claims. In practice that means reserved rights are quantified inside a general stream adjudication alongside every other claim in the basin.

Most large tribal claims are resolved by negotiated settlement ratified by Congress rather than by decree. A settlement can deliver what litigation cannot: funding for storage and delivery works, authority to lease water off reservation, subordination arrangements protecting existing users, and a final waiver of further claims. Construction of the resulting infrastructure is a federal action carrying its own procedural obligations, described under environmental review and the choice between an exclusion, an assessment and a full statement. Where the basin crosses a state line, the settled quantity must still fit within the state's share under a compact or an equitable apportionment decree, which is a ceiling no federal reservation can lift.