- Union Slough is all that remains of a preglacial riverbed. The area is a connection or "Union" between two watersheds; that of the Blue Earth river of Minnesota and the East Fork of the Des Moines River. The terrain is nearly flat in which the flow of the water may be determined by the direction of the wind.
The refuge is on the eastern edge of the Northern Great Plains. Common native range plants are bluestem, gramas, Indiangrass, coneflower, butterfly milkweed and leadplant, to name a few.
Water level management and prescribed fire are two major methods of management that are used on the refuge to improve or maintain the habitat for waterfowl and other wildlife species.
The Refuge is a major producer of wood ducks, with approximately 2,500 produced annually.