On the coast, the Savannah River is the shipping channel for the Port of Savannah, the nation's tenth-busiest port for oceangoing container ships, which is operated by the Georgia Ports Authority. The Savannah's major tributaries in the upper stretch are the Broad and Little rivers, which flow into Clarks Hill Lake.
Before emptying into the Atlantic, the Savannah forms a braided network of tidal creeks, salt marshes, and freshwater marshes, much of which constitutes the Savannah National Wildlife Refuge, one of Georgia's prime bird-watching spots.stretch of river north of Augusta is known as the upper Savannah, along which is located Lake Hartwell, the first of three large lakes built by the U. Downstream from Clarks Hill Dam, the middle section of the Savannah begins.
As such, the Savannah is an alluvial stream, meaning that its waters originate in the mountains and the Piedmont and flow across the Coastal Plain to the ocean. Geological Survey river gauge near Clyo, in Effingham County, the Savannah's average annual flow is 12,040 cubic feet per second, one of the largest discharges of freshwater from any river in the Southeast.
The alluvial rivers transport large amounts of sediments, which contribute to the sand deposits on coastal islands, and of nutrients that nourish life in the river. (One cubic foot equals about 7.4 gallons.) The gauge at Clyo, approximately sixty-one miles upstream of the mouth of the Savannah, is the most downstream gauge that records river discharges.
The confluence marks the beginning of the lower Savannah.
In general, the lower Savannah (to the place where Interstate 95 crosses the river) encompasses a more pristine environment, with oxbow lakes, extensive river swamps, bottomland forests, and blackwater tributaries.
The confluence also forms Lake Hartwell, a large reservoir built by the U. Only about 6 percent of the Savannah's entire drainage basin, however, lies within the Blue Ridge.
The rest lies in the Piedmont and in the Upper and Lower Coastal Plain provinces.
Water in the canal, used for power and water supply, feeds back into the Savannah River at various locations.
In 1983 fossilized whale bones dating back 40 million years were discovered during plant construction.
Across the river from Plant Vogtle, in South Carolina, sits the U. Department of Energy's 310-square-mile Savannah River Site, whose five reactors churned out tons of radioactive plutonium and tritium for thermonuclear weapons from the 1950s through the 1980s.
It is known for its high bluffs, some of which were the locations of prehistoric Native American villages.
The river provides drinking water to two of Georgia's major metropolitan areas, Augusta and Savannah, and assimilates their treated wastewater.
It is also a source of drinking water for the cities of Beaufort and Hilton Head in South Carolina and for many smaller municipalities in the basin. The reservoirs regulate the river's flow and provide hydroelectric power, flood control, recreation, and drinking-water storage.