The interaction of groundwater and surface water in coastal environments is complex because of shallow groundwater, the effects of tides, and the marine climate. Rawlins and Kelbe [1991] indicated that because of the shallow depths to groundwater in a coastal aquifer, the effects of precipitation and evapotranspiration need to be especially carefully defined. In a study of shallow ponds on the Atlantic Coastal Plain, Phillips and Shedlock [1993] also indicated that evapotranspiration directly from groundwater had a significant effect on the configuration of the shallow water table near the surface-water bodies.
In a study of the Great Sippewisset Marsh in Massachusetts, Valiela et al. [1978] and Hemond and Fifield [1982] discussed the complex water movement in tidal marshes caused by the interaction of groundwater discharge and tidal flooding. Nevils and Meadows [1988], in a study of a small watershed on a barrier island in South Carolina, indicated that the most critical component in developing a watershed model is the prediction of the time-varying phreatic surface given any tidal and groundwater inflow conditions.
Coastal ponds on barrier islands in North Carolina were the topic of a study by Kling [1986], who indicated that the chemistry of the ponds is determined by groundwater inflow and the marine climate, and that the relative effects of each are different in different ponds. Ponds that are continuous with the water table have a chemical signature that reflects groundwater chemistry, but ponds that are perched on leached dunes have ionic proportions similar to sea water.
Reay et al. [1993] found that subtidal sandy mineral sediments on the eastern shore of Virginia were affected by groundwater discharge more than organic silty-clay sediments. Results of a model indicated that velocity-associated transport of solutes driven by hydraulic heads in the upland is significant and can dominate over diffusive flux in sandy sediment.