Geoelectrical Resistivity Method (ERT) For Identifying and Mapping Saline Water Intrusion Zone In A Coastal Plain Region of Ambon City

Abstract The spatial variability of the degree of salinity of soils and groundwater is a major issue concerning the sustainable management of water resources. The problem is stressed in coastal plain areas where saline bodies of different origin coexist. We present an extensive geoelectrical resistivity dataset collected in the coastal region of Ambon city. The application of ERT (electrical resistivity tomography) method is to identify lithology below the earth’s surface and determine the dispersion pattern of seawater intrusion in the research area. The area of ERT survey is located approximately 12 m from the coastline using three measurement lines of Wenner Schlumberger electrode configuration. The length of line 1 is 300 m in the south north direction, and the length of line 2 and 3 is 100 m each in the east-west direction. The electrode on line 1 is 10 m and the electrode spacing on line 2 and 3 is 5 m. The 2D resistivity modeling results show a low value resistivity anomaly zone which is interpreted as a water saturated region. The measurement results of electric surveys cannot be interpreted uniquely. Misinterpretation of the analysis results should be minimized by studying the restriction and limitation of the analysis method among other factors. It is recommended that results of other investigations be used to support this evaluation. The resistivity interpretation results are synchronized with the TDS (total dissolved solid) distribution value, allowing for the potential for seawater intrusion into Passo coastal groundwater. The dispersion pattern of subsurface seawater intrusion zones in the study area is sparse. This has resulted in the aquifer layer being interpreted as having been polluted by seawater intrusion with a resistivity ranging from 1.0 - 4.5 Ωm at depths up to 5.0 m with the direction of flow movement from East to West whose distribution is concentrated in the West.