Moreau River

River, formed by the confluence of several headstreams in Butte and Harding counties, northwestern South Dakota, U.S. It flows about 290 mi (470 km) east through the Cheyenne River Indian Reservation, where it receives several north-bank tributaries (including Thunder Butte and Little Moreau), to the Missouri River south of Mobridge. The lower Moreau Basin was inundated by