Mapping of salt-water intrusion by geoelectrical imaging in Carey Islands

Groundwater is an essential and vital resource in all countries. A number of factors can affect the quality of a groundwater aquifer, such as contamination by salt-water intrusion or by toxic industrial chemical waste. These pollutants pose common environmental problems that have created the need to find suitable methods for monitoring the extent of such environmental damage .The advent of fast computing technologies permitted a broad use of the electrical resistivity tomography for environmental purposes .This study aims to investigate the saltwater intrusion in the coastal alluvial aquifer at Carey Island, state of Selangor in Malaysia, by using electrical resistivity method. The purpose of this study is to map the subsurface salinity distribution. Two dimensional electrical resistivity survey was conducted using wenner electrode configuration. The data processing was made by Geoplot3 Res2dinv inversion program and the obtained results were analyzed and correlated with the available boreholes data and as a result, the ground water potential map was created using GIS. The resistivity images yielded useful information about the geometry of saltwater body. The saltwater intrusion was detected at shallow depth around 10m and extending down to more than 40m.The resistivity data were consistent and showed good correlation with the borehole lithologic cross sections, proving the efficiency of combining the two methods in solving environmental problems. Keywords: Coastal environment, electrical resistivity imaging, saltwater intrusion