Characterisation of Seawater Intrusion in the West Part of Pasuruan Groundwater Basin by Geoelectrical Resistivity and Hydrogeochemical Methods

Pasuruan Regency is one of the areas in East Java that has grown into a medium to large scale of industrial area. Most of these are food and beverage factories that require large amounts of water. Groundwater is the main choice in meeting the need for clean water, because it is better quality than surface water. The entire Pasuruan Regency is included in the Pasuruan Groundwater Basin which is classified as very productive, because of the recharge area is on the high rainfall zone. This paper discusses the results of research on the geometric shape of aquifers in areas where there is a meeting between fresh water and brackish water, also show that the geometry of the aquifer, as well as the boundary between freshwater and saltwater. The research was conducted using the geoelectrical resistivity method in the Rembang and Bangil District areas, with the VES (Vertical Electrical Sounding) measurement method, also based on data from groundwater quality testing in several drilled wells. The result of the research shows that brackish water is indicated by a zone with very low resistivity. Furthermore, this is in accordance with the results of water quality test.