## Facts

- Devil’s Hole, a limestone cavern on federal land in Nevada, contains an underground pool that is habitat for the endangered Devil’s Hole pupfish.
- In 1952, a Presidential Proclamation under the Antiquities Act added Devil’s Hole to Death Valley National Monument to protect its unusual scientific features, including the pupfish.
- The Cappaerts owned a nearby ranch and, beginning around 1968, pumped groundwater from wells drawing from the same aquifer feeding the Devil’s Hole pool.
- Pumping lowered the pool level, threatening to expose a rock shelf used by the pupfish for feeding and spawning.
- The Cappaerts obtained Nevada permits to change water use; federal agencies protested, but the State Engineer granted the permits.
- The United States sued in federal district court seeking to limit pumping to protect the pool level needed to preserve the monument’s scientific values.
- The district court issued a permanent injunction restricting pumping to prevent the pool from falling below a specified minimum elevation; the Ninth Circuit affirmed.

## Issues

1. Whether the 1952 national monument reservation implicitly reserved unappropriated water sufficient to accomplish the reservation’s purposes.
2. Whether an implied federal reserved right may include groundwater necessary to maintain the Devil’s Hole pool.
3. Whether the Desert Land Act of 1877 and state water law required the United States to obtain rights only through state procedures, rather than through federal reserved rights.
4. Whether the United States was estopped from asserting reserved water rights based on prior dealings and land exchanges.

## Decision

- The Supreme Court unanimously affirmed.
- The Court held that the 1952 reservation implicitly reserved unappropriated appurtenant water sufficient to maintain the pool level necessary to protect the monument’s scientific values, including the pupfish.
- The reserved right could reach groundwater where groundwater protection was necessary to fulfill the reservation’s purposes.
- The Desert Land Act did not eliminate federal reserved water rights; those rights arise under federal law, vest on the reservation date, and are senior to later state-law appropriations.
- The injunction was proper because it limited pumping only to the extent necessary to maintain the minimum water level required for the reservation’s purposes.
- The United States was not estopped; reserved rights arise by operation of law upon reservation and were not shown to have been relinquished.

## Legal Principles

- When the United States reserves land from the public domain for a federal purpose, it implicitly reserves unappropriated water necessary to accomplish that purpose.
- Federal reserved water rights vest on the date of the reservation and have priority over subsequent state-law appropriations.
- Reserved rights are measured by the reservation’s purposes and extend only to the quantity of water necessary to serve those purposes.
- Reserved rights may include groundwater when groundwater withdrawals would impair the federal reservation’s purposes.
- State water law governs unreserved waters, but cannot defeat federal reserved rights.
- Estoppel does not bar assertion of federal reserved rights absent an express relinquishment or legally sufficient basis to bind the United States.

## Conclusion

The Court sustained a narrowly tailored injunction protecting the minimum water level needed to preserve a national monument’s scientific resources, holding that the United States held senior, federally created reserved rights that included groundwater necessary to prevent impairment of Devil’s Hole and its pupfish habitat.


Cappaert v. United States, 426 U.S. 128 (1976)