Water resources data for the 1999 water year for South Carolina consist of records of stage, discharge, and water quality of streams; stage and contents of lakes and reservoirs; and ground-water levels. This report contains discharge records for 118 gaging stations; stage-only records for 38 gaging stations; stage and contents for 17 lakes and reservoirs; water quality for 42 gaging stations; and water levels for 54 observation wells. Also included are data for 53 crest-stage partial-record stations and discharge measurements at 6 miscellaneous sites. Additional water data were collected at various sites, not part of the systematic data collection program, and are published as miscellaneous investigations of water quality. These data represent that part of the National Water Data System collected by the U.S. Geological Survey and cooperating State and Federal agencies in South Carolina.