Managed Freshwater Impoundments


Managed freshwater impoundments are simply 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 impounded for the purpose of rice culture during the 18th and 19th centuries. The Fish and Wildlife Service has maintained this historic dike system and continues to manage the impoundments for the purpose of providing wintering habitat for waterfowl. Prescribed burning and water level control are two 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. 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 through careful manipulation of water levels. The Freshwater Diversion Canal, constructed in 1978, borders the wildlife drive to the east and plays a vital role in managing the refuge impoundment system. The canal was part of a U.S. Army Corps of Engineers' project to mitigate for increased salinity levels in the lower Savannah River due to a past harbor deepening. It allows freshwater to be pulled from further upstream in the Savannah River, where saltwater intrusion has not occurred, and distributed to refuge impoundments and neighboring private plantations.