Isotope hydrological study of Pulau Langkawi, Malaysia

Abstract

A survey on the stable isotopes and radioisotopes of Pulau Langkawi have been carried out between 1985 and 1989. Groundwater, river water, spring water and sea water were sampled every year whereas rain water was sampled on a monthly basis. The monthly rainwater showed variation in stable isotopes content. But the groundwater response to this variation is very slow with an average 18 0 value of -6.5%0. From the prepared models and based on the 18 0 value, the global minimum turnover time for Pulau Langkawi is between eight to ten months. The Meteoric Water Line for Langkawi was established as oD = 8.0 18 0 + 13.7. Based on the stable isotopes and physico-chemical data, the wells are locally recharged by rainwater. Some of the wells are also recharged by nearby rivers. At the present rate of pumping there would be no intrusion of sea water into the studied aquifers. The high chloride content in some wells are of local feature, due to evaporation. The chloride content at hot springs may originate from mixing with sea water.