Continuous-Resistivity Profiling For Coastal Ground-Water Investigations: Three Case Studies

Abstract

Continuous-resistivity profiling (CRP) was used at three sites to investigate submarine groundwater<br>discharge (SGD) and to delineate the subsurface saltwater/freshwater interface. At the first site, in<br>Georgetown, South Carolina, CRP was used to locate possible areas of SGD in the Winyah Bay estuary.<br>The data show evidence of SGD in the Pee Dee River, feeding into Winyah Bay, at approximately the<br>location of the forest/marsh boundary. In Waquoit Bay, Massachusetts, CRP was used to further map<br>the extent of SGD already measured by sea floor seepage meters and to delineate the subsurface<br>saltwater/freshwater boundary. The data show evidence for a focused ground-water plume beneath the<br>bay that may extend 350 meters (m) out from the shore. Finally, CRP was used in Orleans,<br>Massachusetts, to verify a ground-water model prediction of freshwater-saturated sediments underlying<br>an area of Cape Cod Bay, just west of Rock Harbor. The data support the prediction of freshwatersaturated<br>sediments beneath the bay. Results from all three sites show the value of CRP in coastal<br>ground-water investigations.