## Facts

- Arizona law treated running waters as public and subject to appropriation for milling, mining, and irrigation under a prior-appropriation regime.
- Gillespie, a downstream farmer, and his predecessors had diverted Gila River water for irrigation since about 1872; continued irrigation depended on usable water.
- Arizona Copper operated upstream mines and concentrators using tributary waters; as operations expanded after about 1885, it discharged mine wastes (slimes, tailings) into waterways.
- The wastes moved downstream into irrigation ditches and onto farmland, depositing harmful materials that interfered with irrigation and damaged crops and soil.
- The injury was found to be serious, continuous, and increasing over time.
- Gillespie sought equitable relief to restrain the upstream pollution; the territorial courts granted and then modified an injunction to allow installation of effective remedial works while still requiring prevention of contamination.

## Issues

1. Under Arizona’s prior-appropriation statutes placing mining and irrigation uses on equal footing, may an upstream mining appropriator degrade water quality to the injury of downstream agricultural appropriators?
2. When stream pollution is a continuing nuisance causing special injury to a particular appropriator, may a court of equity grant an injunction despite the scale or public importance of the mining operation and the fact that others are also affected?

## Decision

- The U.S. Supreme Court affirmed the territorial supreme court’s decree.
- The Court held that mining and irrigation appropriators stand on the same plane; no statutory priority permitted mining to injure irrigation users.
- The Court held that an appropriator’s right is limited to necessary use and does not include destroying water quality to the continuing injury of other appropriators.
- The Court held that the pollution constituted a nuisance as to downstream appropriators, and Gillespie could sue because he suffered a special injury distinct from the public at large.
- The Court upheld injunctive relief, including the decree’s allowance for modification upon construction of effective remedial measures to prevent contamination.

## Legal Principles

- Under a prior-appropriation system that authorizes multiple uses without ranking them, lawful users have equal standing; the magnitude or importance of one user’s enterprise does not excuse harm to another’s rights.
- The “necessary use” limitation on appropriative rights applies to water quality as well as quantity; an appropriator may not use water in a way that destroys its quality for other appropriators.
- A public nuisance may also be a private nuisance; a plaintiff who suffers a special, particularized injury may seek equitable relief even if many others are also harmed.
- Equity may enjoin a continuing nuisance when the record shows ongoing or irreparable injury to the complaining party and does not justify denying relief based on claimed hardship to the defendant; decrees may permit modification upon effective abatement measures.

## Conclusion

The Court held that upstream mining operations may be enjoined from polluting public waters where the contamination continuously injures downstream appropriators, because prior-appropriation rights are bounded by necessary use and protect water quality as well as quantity, and a specially injured appropriator may obtain equitable relief.


Arizona Copper Co. v. Gillespie, 230 U.S. 46 (1913)