 The Bois de Sioux River flows northward along the county's west border.The Rabbit River flows westward through the lower part of the county and discharges into the Bois de Sioux on the county's lower west border.The Otter Tail River flows west-northwestward through the central part of the county and merges with the Bois de Sioux at Breckenridge to form the Red River, which continues to flow along the county's west line northward toward the Hudson Bay in Canada.