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. 

Colorado River Compact, 1922 -- Divides the basin at Lee Ferry, AZ. Provides that the upper basin states may use 7.5 million acre feet annually.

Upper Colorado River, 1948
-- Apportions 14% of the water allocated in the Colorado River Compact to Wyoming.

Amended Bear River, 1978
-- Provides for administration of flows and storage between Utah, Idaho, and Wyoming.

Belle Fourche River, 1943
-- Allocates new uses after 1943, 10% to Wyoming and 90% to South Dakota.

Snake River, 1949
-- Wyoming may divert 4% of the ID-WY stateline flow for post-1949 uses.

Upper Niobrara River, 1962
-- Restrictions on storage in larger (over 500 acre feet) facilities.

Yellowstone River Compact, 1950
-- Allocates the flows of the Powder, Tongue, Bighorn and Clarks Fork Rivers between Montana and Wyoming.