The State Engineer is charged with administering and overseeing all matters involving Wyoming's interstate and intrastate streams and rivers. A primary objective of the agency is to safeguard the State’s current and future water supplies by preserving Wyoming’s ability to use and develop our water allocations under our interstate compacts and court decrees. The Interstate Streams Division provides technical and policy support for water allocation and administration issues associated with these governing compacts and decrees. The Water Planning activities of the agency are also coordinated in this Division.
The rights of states to the waters of interstate streams may be settled by decrees of the Courts of the United States or by interstate compacts which are agreements negotiated between states dividing the waters of interstate streams. The rights of Colorado and Wyoming to the waters of the Laramie River and the rights of Colorado, Wyoming and Nebraska to the waters of the North Platte River have been established by decree of the United States Supreme Court. The rights of Wyoming and Idaho water users on Teton Creek and South Leigh Creek have been settled by a decree of the United States District Court for the District of Wyoming. Wyoming's rights to the waters of the Bear River, Belle Fourche River, Colorado River (Green River, Little Snake River, and Henry’s Fork of the Green River), the Niobrara River, the Snake River, and the Yellowstone River (Clarks Fork of the Yellowstone River, Big Horn River, Tongue River and Powder River) have been settled by interstate compacts. International treaties can also affect Wyoming where some of the water that rises in Wyoming eventually finds its way to another country. This is the case with the Colorado River, of which the Green River is a major tributary.