Wyoming v. Colorado

Background

The State of Wyoming sued Colorado and its water users, saying Colorado had departed from an earlier Supreme Court decree about how much water each State and their irrigators could take from the Laramie River and its tributaries. The earlier decree had fixed specific annual amounts for several Colorado claims (including Skyline ditch, meadowland claims, the Wilson Supply ditch, and the Laramie-Poudre tunnel) and reserved remaining flow for Wyoming’s older appropriations. Wyoming asked the Court to stop further departures and to enforce the earlier decree.

Reasoning

The Court examined each claimed departure. It found some Colorado diversions that were not recognized by the decree but accepted Colorado’s promise not to resume those diversions, so no injunction was needed there. The Wilson Supply ditch appropriation from Deadman Creek was held to have been properly recognized (2,000 acre-feet) and not exceeded. The Court concluded the meadowland appropriations were being taken in far larger amounts than the decree’s 4,250 acre-feet and that the flooding practice was wasteful; the decree’s phrase “to divert and take” was read to mean the amount taken at the headgates. Skyline and tunnel diversions were treated differently: the tunnel closely matched its allotment and the Skyline diversions were permissible under transfers and state approval. Because meadowland excesses caused the aggregate overuse, the Court granted an injunction limiting meadowland diversions to 4,250 acre-feet measured at headgates and kept the case open to address measuring and recording if the States cannot agree.

Real world impact

Colorado must curb meadowland irrigation to the decree amount, and Wyoming’s older rights get protection. Many trans-mountain diversions remain allowed when made with Colorado’s approval or by transfers. The Court encouraged the two States to cooperate on better measuring methods but left open the option for a future court order if agreement cannot be reached.