Moreau River (South Dakota)

The Moreau River is a tributary of the Missouri River, approximately 200 miles (320 km) long, located in northwestern South Dakota, USA. Rising in Harding County, it flows generally eastward through Perkins and Dewey Counties before joining the Missouri River in Walworth County, within Lake Oahe, a reservoir created by the Oahe Dam.

The river's drainage basin is characterized by semi-arid grasslands and badlands topography. The Moreau River is known for its highly variable flow, experiencing significant fluctuations depending on precipitation patterns and seasonal runoff. During periods of heavy rainfall or snowmelt, the river can experience flash floods.

The Moreau River valley is sparsely populated, with ranching and agriculture as the primary land uses. Historically, the area was inhabited by Native American tribes, including the Lakota Sioux, who relied on the river for water and sustenance. The river is named after Pierre Moreau, a French fur trader who operated in the area during the early 19th century. The Moreau River is also a site for recreational activities, including fishing and canoeing, although access can be limited due to fluctuating water levels and private land ownership. The river's water quality is affected by agricultural runoff and erosion.