The Savannah River orginates in Hart County at the confluence of the Tugaloo River and Seneca River (Seneca is in South Carolina). This confluence also forms Lake Hartwell. From Lake Hartwell the Savannah River flows southward for over 300 miles, forming the Georgia/South Carolina border. It empties into the Atlantic Ocean near the city of Savannah. Along with the Tugaloo River, the Broad River is also a tributary of the Savannah.