Colorado v. New Mexico - 459 U.S. 176, 103 S. Ct. 539 (1982)

Rule:

The laws of the contending states concerning intrastate water disputes are an important consideration governing equitable apportionment. When, both states recognize the doctrine of prior appropriation, priority becomes the "guiding principle" in an allocation between competing states. But state law is not controlling. Rather, the just apportionment of interstate waters is a question of federal law that depends upon a consideration of the pertinent laws of the contending states and all other relevant facts.

Facts:

The Vermejo River -- which originates in southern Colorado but is located primarily in New Mexico -- is at present fully appropriated by users in New Mexico. Colorado seeks an equitable apportionment of the river's water in order to divert water for proposed uses. The Special Master, after a trial, recommended in his report that Colorado be permitted a diversion of 4,000 acre-feet per year. The Special Master, recognized that strict application of the rule of prior appropriation would not permit any diversion. In applying the principle of equitable apportionment, however, he did not focus exclusively on the rule of priority, but apparently rested his recommendation on the alternative grounds that New Mexico could compensate for some or all of the Colorado diversion through reasonable water conservation measures, and that the injury, if any, to New Mexico would be outweighed by the benefit to Colorado from the diversion. New Mexico filed exceptions to the Special Master's report.

Issue:

Did the report of Special Master recommending equitable apportionment of river's water between Colorado and New Mexico contain sufficient factual findings?

Answer:

No

Conclusion:

 In remanding the matter to the master, the court in general agreed with the application of the equitable apportionment doctrine to the case, but found the factual findings deficient. The court held that the use of water from an interstate river was not ruled by a strict application of the prior appropriation doctrine, but was subject to the rule of equitable apportionment. The court agreed that both the availability of conservation measures and a weighing of the harm and benefits that would result from the diversion were factors relevant to the determination of a just and equitable apportionment.