Most of the southern three-quarters of Hart County is located in the Upper Savannah River sub-basin of the larger Savannah River basin, with the exception of two slivers of the county, south of Royston and west of Bowersville, which are located in the Broad River sub-basin of the Savannah River basin. The northern quarter of the county is located in the Tugaloo River sub-basin of the same Savannah River basin.
Most of the southern three-quarters of Hart County is located in the Upper Savannah River sub-basin of the larger Savannah River basin with the exception of two slivers of the county, south of Royston and west of Bowersville, which are located in the Broad River sub-basin of the Savannah River basin. The northern quarter of the county is located in the Tugaloo River sub-basin of the same Savannah River basin.