Groundwater Study in Coastal Region: Hydrogeology and Geochemical Characteristic of an Island in Malacca Strait, Indonesia

Groundwater is the substantial natural resource in Indonesia as it is become the major source of clean water used for drinking and irrigation activities. However, both quality and quantity of this important resource has facing depletion caused by several anthropogenic activities such as excessive pumping, industrial activities and land use changing. In the coastal area, additional problem to the groundwater resource generally had been found contributed by saltwater intrusion. Bengkalis Island located in the Malacca strait is one of the important regions that connecting Indonesia and Malaysia. The area is developing particularly along the coast, those condition eventually resulting in increased of human activities and affecting the amount of clean water demand. Most people in the study area use dug well to obtain groundwater for their daily need, but brackish water had been discovered in the wells that located near the shore as well as in the distance. Geological information of groundwater aquifer was determined from 4 deep boreholes (±80m each) and 12 lines of electrical geophysics. Groundwater level measured from dug as well as bore wells to mapped groundwater flow, several groundwater samples analyzed in laboratory to specify its chemical content used in determination of groundwater quality and isotope examination for groundwater dating. Furthermore, both isotope and electrical geophysics data was used to trace saltwater intrusion phenomenon and boundary. The result of this research project will be use as scientific evidence by local government in regional development, establishing regulation for groundwater and coastal area management to achieve groundwater sustainability.