The Seneca Watershed consists of the following subwatersheds: Lake Jocassee; Lake Keowee; Seneca River; Little River; Twelve Mile Creek & North Twelve Mile Creek; Twelve Mile Creek; Coneross Creek; Eighteen Mile Creek; and Three and Twenty Creek.
The Seneca Watershed is contained within The Salkehatchie River basin. The Salkehatchie River basin originates in the Sandhills region and flows through the Lower Coastal Plain and Coastal Zone regions. The Salkehatchie River joins with the Little Salkehatchie River to form the Combahee River, which empties into St. Helena Sound and the Atlantic Ocean. Also included in this basin grouping are drainages from the Ashepoo River, the Coosawhatchie River, Broad River, and the New River. The entire Salkehatchie River basin encompasses 2,127,766 acres of which 35% is forested land, 16% is forested wetland, 15% is agricultural land, 14% is scrub land, 10% is nonforested wetland, 7% is water, 3% is urban land, and 0.4% is barren land. Urban land includes Hilton Head Island and the Beaufort area.*
*Information adapted from the South Carolina Department of Health and Environmental Control (S.C. DHEC) website.