Subsurface investigation of seawater intrusion and its impact to the domestic water fulfillment in Pekalongan City, Indonesia

Abstract

The increasing of population growth in the Coastal Area of Pekalongan City has caused serious problem to the domestic water supply. It was getting worst due to seawater intrusion phenomenon. This research aims to investigate seawater intrusion using geophysical method and observe its impact to the domestic water fulfillment. Three sections of 2D resistivity were run approximately 250 meters'perpendicular from the coast line. The resistivity data were processed using RES2DINV software. We also did aninterview to 90 householdsto find out the impact of seawater intrusion in domestic water usage. The result showed that seawater has intruded up to 800 meters from the coast (represent with very low resistivity, <5 Ωm) and increased groundwater salinity significantly to a depth of 13 meters.Nearly everyhousehold in the North part of Pekalongan City could not use groundwater to fulfill their domestic neededdue to the massive seawatercontamination. They had a big dependency of water supply from the government drinking water company even with poor quality. Preventive mitigation action is really urgent to be done in order to reduce the future risk of seawater intrusion in the coastal area.