Integration of Electrical Resistivity Tomography (ERT) and Induced Polarization (IP) methods to observe seawater intrusion in Sungai Nipah Village, Mempawah Regency

Abstract

Sungai Nipah Village is one of the coastal areas of Mempawah Regency, where most people utilize dug wells to meet their clean water needs. The problem faced by the community is that the clean water from the drilled well still has a brackish to salty taste. This study aims to observe seawater intrusion that is estimated to cause the problem based on the distribution of resistivity and chargeability values in the subsurface. The methods used are electrical resistivity tomography (ERT) and induced polarization (IP). The field measurements used a Wenner-Schlumberger configuration with three lines that have a length of 200 m each. The resulting research showed that the study area in Sungai Nipah village is prone to seawater intrusion. The seawater intruding the shallow unconfined aquifer is indicated by resistivity and chargeability values of less than 1 Ωm and 5 ms – 25 ms, respectively. The aquifer layer is composed of sand and clay at a depth of about 13 to 17 m. The seawater intrusion extended from the southern part of the study area to the north and covered about half of the study area.