The St. Francis River basin is located in southeast Missouri in Iron, St. Francois, Madison, Wayne, Washington, Ste. Genevieve, Bollinger, Stoddard, Butler, and Dunklin counties (Figure Lo01). The river originates in northeast Iron County, on a divide that separates the Black, Big, and St. Francis river drainages, and flows 25 miles northeasterly around the St. Francois Mountains uplift. The river then turns south and flows 200 miles to the Missouri/Arkansas border, and then continues 207 miles through Arkansas and into the Mississippi River. The Floodway Ditches drain a portion of the St. Francis River basin. They contribute to the St. Francis River in the state of Arkansas and were not included in this document.
The St. Francis River flows through Wappapello Lake, which is situated near the center of Missouri's portion of the basin. Major tributaries to the river are Little St. Francis River and Big Creek above the Wappapello Dam, and Mingo Ditch and Dudley Main Ditch below the Wappapello Dam.