Graham Creek, a tributary of the Souris River, is a stream that flows from Saskatchewan near Maryfield into Manitoba where it meets the Souris River on the west side of Melita, Manitoba. The Souris River, in turn, drains into the Assiniboine River, which is part of the Red River drainage basin in a region called the Prairie Pothole Region of North America. That region extends throughout three Canadian provinces and five U.S. states. It is also within Palliser's Triangle and the Great Plains ecoregion.