The Supreme Court in Montana v. Wyoming –U.S.–, 131 S.Ct. 1765 (2011), rejected Montana’s claim that Wyoming’s usage of water depleted the amount of water available to it under the Yellowstone River Compact between Montana and Wyoming. Montana contended that Wyoming breached Article V(A) of the Compact which provided that “appropriative rights to the beneficial uses of the water of the Yellowstone River System existing in each signatory State as of January 1, 1950, shall continue to be enjoyed in accordance with the laws governing the acquisition and use of water under the doctrine of appropriation.”
Better farming techniques of irrigation developed since 1950 have allowed Wyoming farmers to divert the same amount of water but have resulted in reducing the amount of water returning to the river as run off. It is as though Wyoming farmers had been using leaky buckets for irrigation that returned water to the river in 1950, but later bought new buckets that didn’t leak, giving the farmers more water and more use of it, reducing the amount of water returned to the river and available to the downstream Montana users.
The concept the Court focused on was “beneficial use” and diversion, not depletion. The Court considered appropriation as a water right that once it is perfected, “is senior to any later appropriators’ rights and may be fulfilled entirely before those junior appropriators get any water at all.” Thus in the Court’s view, as long as Wyoming farmers diverted the same amount of water in 2011 as in l950, they did not violate the compact, even if the diversion caused depletion of the water resources.
The sole dissent was Justice Scalia who focused on the notion of depletion rather than diversion since that was the word used in the Compact. He noted that “beneficial use” in the Compact was defined as one “by which the water supply of a drainage basin is depleted when usefully employed by the activities of man.” He argued that the majority had essentially written the word out of the Compact. There was no question that Wyoming farmers depleted the river by their better irrigation techniques.
As the world faces depletion of fresh water resources by declining glaciation, increased drought in drought-prone regions, and increases in population, the common law adage of “first in time, first in right” may cause real problems for downstream users who may face increased salinity and reduced water volume.