Geography of South Dakota - Rivers and Lakes

Rivers and Lakes

The Missouri River is the largest and longest river in the state. Other major South Dakota rivers include the Cheyenne, the James, the Big Sioux, and the White. Essentially all of South Dakota's rivers are part of the Missouri River Valley. Dams on the Missouri River create four large reservoirs: Lake Oahe, Lake Sharpe, Lake Francis Case, and Lewis and Clark Lake. Hydroelectricity generated from power plants at the dams provides approximately half of the electricity used by South Dakotans.

The vast majority of South Dakota's natural lakes are located in the eastern half of the state, and most are the product of the most recent ice age. The title of largest natural lake is somewhat disputed; Lake Thompson is larger than Lake Poinsett, but Lake Poinsett has maintained its current size for a much longer period of time. Other major natural lakes include Lake Kampeska, Waubay Lake, Lake Madison, Lake Whitewood, and Lake Herman. Additionally, two large lakes, Big Stone Lake and Lake Traverse, form part of the border between South Dakota and Minnesota. The continental divide separating the drainage basin of Hudson Bay from that of the Gulf of Mexico is situated between these two lakes.