Santee River The Santee River is a river in South Carolina in the United States , long . The Santee and its tributaries provide the principal drainage and navigation for the central coastal plain of South Carolina , emptying into the Atlantic Ocean approximately from its farthest headwater on the Catawba River in North Carolina . Much of upper river is impounded as the expansive , horn - shaped Lake Marion reservoir , formed by the - long Santee Dam . It was built during the Great Depression of the 1930s as a Works Progress Administration ( WPA ) project to provide a major source of hydroelectric power for the state . Description . The Santee is formed in central South Carolina southeast of Columbia by the confluence of the Wateree and Congaree rivers . It flows southeast for before entering the northwest corner of Lake Marion , which stretches in a long wide arc to the southeast for approximately to Santee Dam . A navigable diversion canal first built in the 1970s at the southern tip of the lake connects to Lake Moultrie , a reservoir on the nearby Cooper River . The modern canal is operated by Santee Cooper as part of the larger hydroelectric project on both rivers . The dam was finished in 1941 . Downstream from the reservoir it flows east , then southeast , forming the northeast boundary of Francis Marion National Forest . Approximately from its mouth it bifurcates into two channels , called the North Santee and South Santee , that flow parallel and separated by approximately , creating Cedar Island . The two channels reach the ocean at Santee Point , approximately south of Georgetown , and not far from the mouth of the Pee Dee River . History . The river was named by early English settlers after the Santee tribe , which inhabited areas on the middle part of the river . The first European contact was by a Spanish party led by Lucas Vázquez de Ayllón in 1526 . The Spaniards called the river the " Jordan " in honor of the Jordan River . After suffering a defeat by the English and their allies during the Yamasee War in 1715 – 1716 , the Santee were relocated . Many were shipped as slaves to the West Indies , opening up the river for British settlement as part of the Carolina Colony . Most of the Siouan peoples had migrated into the upper Midwest before European encounter . In the late 18th century , the upper river was the site of the homestead of Francis Marion , a patriot of the American Revolutionary War . The original site of his homestead has been flooded by Lake Marion , which is named in his honor . Construction of the - long Santee Canal , linking the river to the Cooper , was begun in 1793 and finished in 1800 . It allowed direct water transportation between the Upcountry of central South Carolina and Charleston , at the mouth of the Cooper and the harbor . The canal operated for 50 years before being made obsolete by the introduction of railroads . During the Great Depression , the state of South Carolina created the Santee Cooper power utility . The main source of electric power for the utility came through federal construction during the administration of President Franklin D . Roosevelt of a hydroelectric project inland from Charleston . Starting in 1939 , the Santee River was dammed , forming lakes Marion and Moultrie , and diverting the river ' s flow into the Cooper River through a hydroelectric plant at Pinopolis . The WPA project was completed in 1941 . Though the project succeeded in providing cheap electricity to modernize rural South Carolina , unintended consequence s were changes to the character of both the Cooper and Santee rivers below the project . Deprived of most its water flow , the Santee River became more saline and its ecosystem gradually changed below the dam . The Cooper River received more of the freshwater and sediment loads that used to flow into the Santee and carried them downstream . This has resulted in greatly increasing the dredging costs to keep Charleston Harbor operating as a port . In the 1980s , the Army Corps of Engineers built a diversion canal to send some water back into the Santee , partially mitigating this problem . Crossings . This is a partial list of crossings of the Santee River