Step-wise Overlay Technique for the Mapping of Unconfined Groundwater Potential Zone in Tectonically Controlled Landforms

Abstract

The existence of unconfined groundwater in tectonically-controlled volcanic landforms is continuous and discontinuous as in alluvial landforms. DEM-NAS is a product available all over Indonesia and has the potential for unconfined groundwater mapping. The study was conducted by applying GIS techniques to obtain information on drainage density, TWI (Topographic Wetness Index), slope angle, and lineament density with openly available algorithms. All parameters are put on the map using fuzzy analysis techniques before being combined using a step-wise overlay technique. Classification of unconfined groundwater potential was done based on the value of the merging parameter map. The results of the field verification show that 44 springs are in the potential zone with an area percentage of 68.01%, and 10 springs are in the less potential zone with an area percentage of 31.99%.