Abstract

There is a dynamic interface between fresh groundwater and saline ocean water in coastal regions worldwide, known as the fresh-saltwater interface, where salt and freshwater mix caused by natural and anthropogenic activities. The interface migrates inland in a saltwater intrusion process, which further results in salinization and can have significant economic and ecological impacts. This study has employed geophysical and geochemical techniques to map the extent of salinization of the shoreline aquifers of Kachulu. The geophysical data acquisition and processing of 2D ERT (Electrical resistivity Tomography) was performed using ABEM SAS 4000 and RES2DINV software using a Wenner electrode configuration array. The geophysical survey successfully delineated aquifers with various resistivity values related to recharge and migration processes, including saltwater intrusion in the basin. Evidence from the geochemical study of boreholes and the lake water samples corroborated the ERT result. Elevated EC, turbidity, pH, TDS levels and other chemical parameters measured from the sampled boreholes showed that the salt impairs the inland aquifers through various sources. This study successfully mapped the areas of freshwater aquifers and the extent of the salinity in the aquifers of Kachulu, contributing to sustainable future decisions, planning, and development in the study area.

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School	: School of Natural and Applied Sciences
Issued Date	: 2022

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