Justia U.S. Supreme Court Opinion Summaries

Montana alleged that Wyoming breached Article V(A) of the Yellowstone River Compact ("Compact"), 65 Stat. 666, by allowing its pre-1950 water appropriators to increase their net water consumption by improving the efficiency of their irrigation systems where the new systems employed sprinklers that reduced the amount of wastewater returned to the river, thus depriving Montana's downstream pre-1950 appropriators of water to which they were entitled. At issue was whether Article V(A) allowed Wyoming's pre-1950's water users, diverting the same quantity of water for the same irrigation purpose and acreage as before 1950, to increase their consumption of water by improving their irrigation systems even if it reduced the flow of water to Montana's pre-1950 users. The Court held that Montana's increased-efficiency allegation failed to state a claim for breach of the Compact under Article V(A) where Article V(A) incorporated the ordinary doctrine of appropriation without significant qualification and where, in Wyoming and Montana, that doctrine allowed appropriators to improve their irrigation systems, even to the detriment of downstream appropriators.