Identification of Groundwater Potential Zones in Langkawi Through Remote Sensing and Geographic Information System (GIS) Techniques

Abstract

Water demands in Langkawi Malaysia have risen due to an increase number of tourists each year which resulted in rapid developments of the island. These developments have severely affected the water resources in this small island. In this research, a weighted overlay analysis has been done for detecting groundwater potential zones (GWPZ). Weighted overlay analysis tool was chosen to find the potential of water beneath the earth through the combination of Geographic Information System (GIS) and remote sensing techniques as a solution for water issues in Langkawi Island. Seven factors namely elevation, lineament density, drainage density, geology, slope, soil type and land use land cover (LULC) were produced to create GWPZ map by rank. Firstly, a ranking based on diagram connection between potential groundwater zones influencing factors for GWPZ generation was being used to put a rank of all subclasses in the seven thematic maps. The thematic maps were then adjusted from rank one (1) as low value to five (5) as the highest value. Subsequently, GWPZ was generated by GIS software using weighted overlay analysis tool by overlaying all the seven thematic maps in GIS analysis tool. In the analysis, the output of GWPZ has been validated using existing wells presented as points in Langkawi to verify the relationship between generated GWPZ and existing data. It was found that existing wells satisfyingly overlapped on the moderate and high area of groundwaters in the GWPZ map. For second analysis using the depth of the existing well location, it was found that the depth varies in the same potential area from the generated GWPZ. This study has found that groundwater potential zones technique can interpret the availability of water under the ground area but may not interpret the depth of water below the earth correctly. All in all, using GIS and remote sensing, this research has proven to successfully detect groundwater in Langkawi and can be a reference for future projects for a sustainable water management in Langkawi Island.