Facts
- New Jersey invoked the Supreme Court’s original jurisdiction and sought to enjoin New York and New York City from diverting water from the Delaware River watershed to supply New York City.
- New York proposed diverting up to 600 million gallons per day from non-navigable tributaries at the Delaware’s headwaters and transferring the water into the Hudson River watershed.
- The Delaware River serves, in stretches, as a boundary involving New York, Pennsylvania, and New Jersey before reaching the Atlantic.
- New Jersey alleged the diversion would impair navigation, degrade water quality and sanitation, increase salinity downstream (affecting oyster fisheries), interfere with recreation, and constrain future hydroelectric development.
- Pennsylvania intervened to protect its present and potential interests in the Delaware River.
- A special master took extensive evidence; expert testimony supported findings that the proposed diversion would not impair navigability and would not materially harm sanitary conditions at the proposed level.
Issues
- Whether allocation of an interstate river between states is governed by strict private riparian rights or by equitable apportionment.
- Whether New Jersey was entitled to a complete injunction barring New York’s proposed diversion to another watershed.
- What limitations and conditions, if any, were required to protect other states’ interests, including navigation, sanitation, fisheries, recreation, and future uses.
Decision
- The Court applied equitable apportionment, not strict riparian rules, because the controversy was between states.
- The Court denied a total injunction and permitted New York’s diversion only subject to substantial regulation and curtailment.
- The Court accepted the master’s finding that navigability would not be impaired for purposes of the decree, while recognizing federal supremacy over navigation.
- The Court rejected New Jersey’s claims based on speculative future hydroelectric development as insufficient to justify present relief.
- The Court required conditions, including sewage-treatment-related obligations, to mitigate risks to recreation and salinity-sensitive downstream interests (including oyster fisheries).
- The Court denied Pennsylvania’s request for a present allocation and a river master without prejudice and retained jurisdiction to modify the decree as conditions change.
Legal Principles
- Interstate water disputes between states are governed by equitable apportionment rather than private-law riparian doctrines.
- Diversion of water to another watershed is not per se unlawful; permissibility turns on equitable balancing and reasonable necessity.
- Permitted diversions remain subject to Congress’s paramount authority over navigation and related federal regulatory powers.
- A decree allowing diversion does not create a prior-appropriation-type superior right; interstate water rights remain adjustable under equitable principles.
- Interstate water decrees may impose operational limits and protective conditions and may be modified through retained jurisdiction.
Conclusion
The Court resolved the interstate water controversy through equitable apportionment, allowing New York to divert Delaware River headwaters for municipal supply only under a limited, regulated decree designed to protect downstream states’ concrete interests, while preserving federal navigation authority and the Court’s power to revise the allocation as circumstances change.