Water Budget of a Shallow Aquifer in the Lower Coastal Plain: ACE Basin, SC

Abstract

The expansive tidal salt marshes of South Carolina support a unique and sensitive ecosystem providing environmental and economic value to the coastal community. These tidal ecosystems are often altered by sea level rise through various processes, including the lesser-known stress of saltwater intrusion in groundwater systems. The goal of this research was to measure the baseline groundwater dynamics of an undeveloped tidal saltmarsh. Groundwater wells were installed along transects from the upland into the marsh and a culminating water budget of the watershed was developed. Analysis of water table dynamics showed that in the upland zone, evapotranspiration and precipitation were the dominant processes, whereas in the marsh zone and the uplands directly adjacent to the marsh, water table fluctuations were dominated by tides. An influencing feature for the site was the large tidal creek (Big Bay Creek), which is a tributary of the South Edisto River. The cut bank of Big Bay Creek was adjacent to the south end of the study site where tidal influence on the shallow groundwater was observed. The location of an ephemeral stream through the site was considered as a potential pathway for saltwater intrusion into the uplands, yet this was not confirmed. Groundwater response rates were likely influenced by the presence of fine-grained, well-drained sandy soils. Application of this research will assist coastal resource managers identifying pathways of marsh migration as driven by future seal level rise.