The North Inlet Estuary and the adjacent lower northeastern section of the Winyah Bay Estuary were designated as part of the National Estuarine Research Reserve System in 1992. The North Inlet-Winyah Bay (NIW) NERR's water quality monitoring program began on October 25, 1993. The System-Wide Monitoring Program (SWMP) was initiated in 1995 to set protocols for monitoring the estuarine environment at all NERR sites. Water quality data for the NIW NERR were collected under these protocols throughout the rest of the dataset. Four sites were chosen to best represent pristine and impacted locations within the reserve and data were collected using dataloggers automated instruments used to record water quality indicators. The Oyster Landing site is located near the center of the reserve and the Clambank site is located on a waterway that receives run-off from the undeveloped area of the reserve, both are considered pristine. The Debidue Creek and Thousand Acre sites are located in waterways that receive run-off from heavily developed areas. Dataloggers were mounted in 4 inch diameter PVC pipes, strapped to treated 2 inch by 6 inch boards, and then attached with stainless steel bands to a piling at each site. The PVC pipes that house the dataloggers have two large cut out "windows" near the bottom to give the probes direct contact with the water column. A stop bolt placed through the PVC pipe below the windows keeps the datalogger exactly one foot (30 cm) above the creek bottom. Measurements of water temperature, specific conductivity, salinity, dissolved oxygen (percent saturation and mg/L), water level, pH, and turbidity were taken every 30 minutes over collecting periods of approximately two weeks. The two-week sampling period was chosen based on the expected battery life of the datalogger and to minimize the impact of biofouling on the individual probes. At the end of the collecting period the dataloggers were brought to the laboratory, the data were downloaded, and the instruments were cleaned and recalibrated following the relevant service manual and SWMP protocols. Post-calibration readings were also taken from each instrument in fresh standard to determine if any of the probes exhibited drift. After approximately 24 hours of down time, the dataloggers were re-deployed. Down time was minimized whenever possible by using extra dataloggers in rotation for back-to-back deployments. This database and metadata document are the Baruch Institute's versions, are independent of the NERR/CDMO versions, and follow Baruch's quality control and assurance procedures in addition to NERR SWMP protocols.