Montana v. Wyoming

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It is somewhat rare that the U.S. Supreme Court delves into the world of western water law, but it recently did so in a case between the states of Montana and Wyoming. This case is not an appeal of any decision by a lower court, because when one state sues another, the case goes directly to the U.S. Supreme Court for determination. The central issue in the case is whether Wyoming violated the Yellowstone River Compact because Wyoming water users had converted from flood irrigation to sprinkle irrigation, which increased the consumption of water in Wyoming beyond historic (pre-1950) levels.

Wyoming, Montana, and North Dakota entered into the Yellowstone River Compact in 1951, and Congress then ratified the Compact. The Compact provided that beneficial users of water on the Yellowstone River system with priority dates before January 1, 1950 "shall continue to be enjoyed in accordance with . . . the doctrine of appropriation." Montana claimed, among other claims, that more efficient irrigation practices were consuming more water on the Wyoming (upstream) side, which left less water for the pre-1950 Montana water rights. Montana based its claims first on general principles of the prior appropriation doctrine, and second on the Compact's definition of "beneficial use."

The Court concluded that, although "the law of return flows is an unclear area of the appropriation doctrine," the general rule allows a water user to increase his irrigation efficiency even if that harms downstream users. First, the injury that a change in water use cannot injure other water users does not apply to changes in crop type or irrigation method, but applies to changes in points of diversion, or place or purpose of use. Second, most western states allow an appropriator to recapture and reuse water on the same acreage as long as it remains on the property and within the water user's control. Thus, the general rule already allows increased consumption through recapture.

The Court also rejected Montana's second claim that the compact itself strictly limited Wyoming to a maximum amount of depletion. The Court indicated that other compacts like the Colorado River Compact expressly limit depletion amounts, but the Yellowstone River Compact does not. Therefore, the Court concluded that the Compact's definition of beneficial use simple acknowledged a preference for consumptive uses rather than nonconsumptive uses.

Ultimately, this case is not binding on any state court, including Utah courts. The Supreme Court specifically acknowledged that state courts control the doctrine of prior appropriation. Nevertheless, the discussion found in the case is instructive of general principles of western water law.

(Click here to read the full text of the Supreme Court's Opinion)