Interstate Compacts and Decrees
As a headwaters state, Wyoming is party to seven interstate compacts and 2 U.S. Supreme Court decrees. In addition to participating in the Commissions that have been established to administer these compacts, the State Engineer also participates in a number of basin- or region-wide water resource groups and associations.
North Platte River, 1945 -- The Supreme Court ruled that Wyoming could irrigate up to 168,000 acres. Natural flow split at the state line 25% to Wyoming and 75% to Nebraska.
Laramie River, 1911, 1922 -- Allows Colorado to divert up to 39,750 acre feet per year.
Teton Creek and South Leigh Creek ("Roxanna" Decree), 1941 -- When the flow naturally available at the state line in either stream declines below specified thresholds, it is split between Wyoming and Idaho apportionment diversions.
Yellowstone River Compact, 1950 -- Allocates the flows of the Powder, Tongue, Bighorn and Clarks Fork Rivers between Montana and Wyoming.