Managed freshwater impoundments are tidal freshwater marshes that have been diked and "impounded" in order to manipulate the vegetation through water control. The impoundments at Savannah NWR were originally used for growing rice during the 18th and 19th centuries.
The US Fish and Wildlife Service has maintained this historic dike system and continues to manage the impoundments for the purpose of providing wildlife habitat, including wintering habitat for migratory waterfowl. Prescribed burning, water level control, and targeted mowing are three management tools used to promote desirable wetland plants and to suppress vegetation that is of less value to migratory birds. Moist soil management, which is used in most of the management units on Savannah NWR, produces the most productive waterfowl habitat.
The 3,000-acre impoundment system is actively managed using 32 water control structures, including 15 rice field trunks (see photo above). A regimen of flooding and draining of the impoundments provides feeding, roosting, and nesting habitat for waterfowl, shorebirds, wading birds, and other wildlife.
In place of rice, which was grown in these impoundments historically, wild foods such as smartweed, redroot, and millet are encouraged to grow.