S.C. Code Ann. § 49-21-20
Following the effective date of this chapter, no person shall withdraw, divert, pump, or cause directly the transfer of either five percent of the seven-day, ten-year low flow, or one million gallons or more of water a day on any day, whichever is less, from one river basin and use or discharge all or any part of the water in a different river basin unless the person shall first obtain a permit from the department.