## Facts

- The Town of Antioch diverted fresh water for municipal supply near the downstream tidal reach of the San Joaquin River where it connects to Suisun Bay.
- Antioch claimed a senior appropriative right based on long-continued diversion and use, including by prescription.
- Multiple upstream entities, including the Williams Irrigation District, diverted substantial quantities of water from the Sacramento River and its tributaries for irrigation and other beneficial uses.
- The upstream diversions reduced downstream freshwater flow, allowing tidal salt water from the Bay to intrude farther upstream and render water at Antioch’s intake too saline for municipal use.
- Antioch alleged the upstream diversions effectively “polluted” its supply by permitting saltwater encroachment, not by introducing foreign contaminants.
- Antioch sought to restrict upstream diversions to preserve enough freshwater flow to keep saltwater below its diversion point.
- A trial court issued a temporary injunction limiting defendants’ diversions during the action; defendants appealed.

## Issues

1. Whether a downstream appropriator near a river’s tidal outlet has a right to compel subsequent upstream appropriators to leave sufficient flow to prevent tidal salt water from moving above the downstream point of diversion.
2. Whether an appropriator’s protectable interest in “purity” against later appropriators extends to salinity increases caused by naturally occurring tidal intrusion triggered by reduced freshwater flow.
3. Whether a municipal appropriator may invoke public or navigational interests to support an injunction controlling upstream diversions.

## Decision

- The California Supreme Court reversed the interlocutory order granting the temporary injunction.
- The court held that an appropriator of fresh water near the outlet to the sea does not acquire a right to require upstream appropriators to leave enough water in the stream to hold back tidal salt water below the appropriator’s diversion point.
- The court rejected Antioch’s reliance on public or navigational interests, explaining such interests are enforceable by the state or the United States, not by a city acting as an appropriator.

## Legal Principles

- Riparian rights are private rights incident to ownership of land abutting a watercourse and are limited to use on the riparian land.
- A water right may be acquired by actual appropriation and use even without strict compliance with statutory procedures.
- A prescriptive appropriator may enjoin later nonriparian upstream diversions that materially impair the appropriator’s prior right to the quantity of water diverted.
- An appropriator is generally entitled, as against subsequent upstream appropriators, to have the water at the point of diversion preserved in its natural purity to the extent necessary for the appropriator’s then-existing beneficial use.
- That protection does not include a right, for an appropriator near a tidal outlet, to mandate river flows sufficient to prevent saltwater intrusion caused by the interaction of reduced flow and natural tidal forces.
- A municipal corporation appropriating water from a navigable stream has no authority to regulate or protect navigation-related public rights; those belong to the state or the United States.

## Conclusion

The court held that a downstream municipal appropriator near a tidal river outlet cannot use appropriative-right doctrines to force upstream diverters to maintain freshwater flows sufficient to repel tidal saltwater intrusion, and it reversed the temporary injunction that had restricted upstream diversions.


Town of Antioch v. Williams Irrigation Dist., 188 Cal. 451, 205 P. 688 (Cal. 1922)