Subsurface Flow in Georgia Coastal Plain

Subsurface flow and infiltration studies conducted on 10 Coastal Plain soils under artificial rain indicated that subsurface flow was the major contributor to streamflow in the Coastal Plain. Water balance analysis indicated that, for all the soils studied, an average of about 42% of the applied rainfall became subsurface flow, with the final infiltration rate varying between 1 and 3 in./h (0.025 and 0.076 m/h). The upland soils have the greatest ability to produce subsurface flow, and the lowland soils have the least. On a 0.849-acre (3.435 m²) watershed, subsurface flow accounted for 28.4% of the total precipitation for a 3-yr period while surface runoff accounted for only 7% of the total precipitation. The subsurface flow occurred in all months except November, with the most prominent events occurring in March and August. Preliminary analyses of the subsurface flow hydrograph characteristics from this watershed generally indicate a quick, sharp peak with a slow recession.