FIELD IDENTIFICATION OF GROUNDWATER POTENTIAL ZONE BY VES METHOD IN SOUTH MALANG, INDONESIA

In order to solve the water scarcity problem in South Malang, East Java, Indonesia, we have attempted to investigate groundwater by assessing the subsurface geology and groundwater potential zones. An attempt had been made to identify the subsurface lithology and aquifer zones by VES (Vertical Electrical Sounding) method in Pagak, Kepanjen, Kromengan and Gondanglegi district. The study area consists of major subsurface litho units like sand, silt, clay, tuff, limestone and andesit. In order to explore the groundwater resources of the study area with an aerial extent of 100 km2, electrical soundings have been conducted by adopting Schlumberger technique in 12 locations with AB/2 200 m and 5 resistivity profiles were acquired. The field data were interpreted and processed qualitatively and quantitatively by using computer software. Considering the geological, geomorphology and hydrogeological conditions the VES interpretation was done. The study has shown that the region is underlain by 5 geoelectric layers within the depth penetrated. The groundwater potential in South Malang reveals four distinct classes (zones) representing ‘Very good', ‘good', ‘moderate' and ‘poor' groundwater potential in the area. From the interpretation result the VES no. 7 (Pagak), and VES no. 9 (Kepanjen) are found to be prospective for groundwater. It's also identified that Groundwater occurs under water table conditions the depth of water table ranges from 5 to 30 m