Plpti

Almost from the time that explorers John C. Fremont and Kit Carson first came upon the Truckee River and Pyramid Lake, disputes have arisen about water rights. In this latest chapter in a hundred-year litigation history, see Nevada v. United States, 463 U.S. 110, 113 , 103 S.Ct. 2906 , 77 L.Ed.2d 509 (1983) (summarizing history), we consider whether diverting water to wetlands in order to sustain wildlife habitat constitutes “irrigation.” We conclude that, within the meaning of the federal court decree governing water rights in the Newlands Reclamation Project, it does not, and we affirm the judgment of the district court.

I

Two rivers flow through the Truckee River Basin, which straddles the California-Nevada border in one of the nation’s most arid regions: the Truckee and the Carson. The Carson River “rises on the eastern slope of the High Sierra in Alpine County, California, and flows north and northeast over a course of about 170 miles, finally disappearing into Carson sink.” Id. at 115 , 103 S.Ct. 2906 . The Truckee River originates in Lake Tahoe, flows north and east into Nevada, and terminates in Pyramid Lake, for which it provides the sole source of water.…