The North Platte River Basin in Wyoming is the most densely populated in the state. The river and its tributaries, the Encampment, Sweetwater, Medicine Bow and Laramie, drain most of the southeastern quarter of Wyoming. The basin covers about 28,000 square miles. The North Platte originates in the mountains of Colorado and flows north towards Casper, Wyoming where it turns towards the southeast and eventually flows into Nebraska.
Several tributaries drain mountainous areas on the eastern continental divide.
Five mainstem federal reservoirs, managed by the U.S. Bureau of Reclamation, have a combined capacity of over 3 million acre-ft to store spring runoff. This storage serves instate and Nebraska irrigators. About 528,000 acres are irrigated in Wyoming. The Laramie River also originates in Colorado and flows north to join the North Platte near Wheatland and has reservoir regulation of flows and extensive irrigation use. Agricultural, industrial, and recreational uses of the river are widespread.