## Facts

- Nebraska filed an original action in equity against Wyoming seeking equitable apportionment of the North Platte River (a nonnavigable stream) and an injunction against alleged upstream irrigation diversions.
- Colorado was impleaded as a defendant; the United States intervened due to federal reclamation projects dependent on North Platte water, including the North Platte Project and the Kendrick Project.
- Nebraska alleged that diversions in Wyoming and Colorado violated the priority of appropriation doctrine applied in the three states and deprived Nebraska of water to which it was equitably entitled.
- Wyoming denied wrongdoing but joined the request for equitable apportionment; Colorado denied excess use and sought apportionment among the three states (with limited exclusions for certain tributary waters).
- A Special Master conducted extensive hearings and submitted a report; the case reached the Court on exceptions to that report, including Colorado’s motions to dismiss for lack of a justiciable controversy.
- The record showed that dependable natural flows during the irrigation season were long over-appropriated and that competing existing and projected uses exceeded available supply.

## Issues

1. Whether the dispute presented a controversy of sufficient character and dignity to warrant the Supreme Court’s exercise of original jurisdiction to apportion an interstate river.
2. Whether equitable apportionment among prior-appropriation states requires strict, literal application of inter-state priority dates.
3. How federal reclamation projects and any asserted federal interest in unappropriated water affect allocation among the states.
4. Whether the Court may decline to act because drafting and enforcing an apportionment decree is administratively difficult.

## Decision

- The Court held that a justiciable interstate controversy existed and rejected Colorado’s attempts to dismiss.
- The Court made an equitable apportionment of the North Platte River among Nebraska, Wyoming, and Colorado.
- The Court held that equitable apportionment among appropriation states does not require literal application of the priority rule; priority is a guiding principle, not an exclusive determinant.
- The Court held it unnecessary to decide the scope of any federal right to unappropriated water because the relevant federal project water rights were obtained in compliance with state law.
- The Court held that allocating water-use entitlements to the states, acting as parens patriae, does not interfere with federal ownership and operation of reservoirs, storage, or power facilities.
- The Court stated that remedial complexity does not justify refusing to perform the constitutional function of resolving serious interstate water disputes.

## Legal Principles

- The Supreme Court may equitably apportion an interstate stream in an original action when over-appropriation and conflicting claims create a concrete, substantial dispute.
- In equitable apportionment among prior-appropriation states, priority of appropriation is an important guide but does not mandate a rigid, date-driven allocation.
- Equitable apportionment considers multiple factors, including physical and climatic conditions, consumptive use, return flows, extent of established uses, availability of storage, waste and its downstream effects, and comparative harms and benefits of limiting uses.
- Federal reclamation project water rights obtained pursuant to state law are treated as definite and enforceable within the same apportionment framework; the Court need not resolve abstract claims to remaining unappropriated water to enter an operative decree.
- The Court will not abstain from adjudicating an interstate water controversy solely because supervising an allocation decree is difficult.

## Conclusion

The Court exercised original jurisdiction to resolve a concrete shortage-driven conflict over the North Platte River by equitably apportioning waters among Nebraska, Wyoming, and Colorado, treating priority as a key but noncontrolling consideration, integrating federally based (state-law) reclamation rights, and confirming that complexity in administering relief does not excuse decision.


Nebraska v. Wyoming, 325 U.S. 589 (1945)