Date of Award
Master of Science in Geology
This study was undertaken to determine the geological and geohydrological conditions of these regions within the study area, the Rhode Island shoreline of Narragansett Bay, which are underlain by saltwater-bearing aquifers, with respect to demonstrating the applicability of the direct current resistivity method and the Ghyben-Herzberg relation. The depth sounding method and the Ghyben-Herzberg relation are both essentially untried under the conditions found in the study area, that is, saltwater intrusion into bedrock aquifers.
Work proceeded by first denoting locations known to have saltwater at depth by virtue of its having been reported in water wells. At selected sites, resistivity depth soundings (with Schlumberger array) were made. The results, plotted as curves, were interpreted by the curve-matching technique with the use of theoretical master curves. The interpretations were then refined by the use of a theoretical curve-generating computer program.
Analysis of the collected field data has demonstrated that the resistivity depth sounding method is indeed applicable to determining the depth of the saltwater interface in the bedrock aquifers and that the indication of saltwater is quite clear in most cases. It is evident then, that a large-scale depth sounding reconnaissance of the study area, for the purpose of developing saltwater wells for use in the marine seafood industry, is a distinctly possible and practical means for determining the depth to the saltwater interface.
Due to the nature of the porosity of the bedrock and a probably lack of vertical communication between fresh and saltwater which seems to be indicated by the resistivity data, the Ghyben-Herzberg relation has been found not to be useful in predicting depth to saltwater within the bedrock aquifers of the study area.
Shipman, Wayne D., "Saltwater-Bearing Aquifers at the Periphery of Narragansett Bay: Geoelectric and Geohydrologic Characteristics" (1978). Open Access Master's Theses. Paper 2024.