Combination of rocks and soil radioactivity measurements and geoelectrical to determine potential groundwater aquifer in Sumbermanjing Kulon village, Pagak, Malang, East Java

The study area is an area with difficulties in fresh water supply. This study aimed to investigate geological characteristics, stratigraphical traps and sub surface geophysical characteristics to identify aquifer existence, depth and distribution. The purpose of this study is to determine the potential location for groundwater drilling to fulfill the needs of fresh water in this area. Stages of activities include topography mapping, geological mapping, soil/rocks radioactivity measurements, geoelectric (resistivity) surveys and potential location determination analysis for drilling. The study area is an area with undulating terrain, lithologically composed with sandstone unit and limestone unit. Radioactivity value of limestone ranged from 30 c/s to 45 c/s, carbonaceous sandstone ranged from 20 c/s to 30 c/s, and tuffaceous sandstone lower than 20 c/s. Based from geoelectrical measurements analysis, lithologically this area divide into 4 rock layers, i.e. limestone (>1000 Ωm), claystone (1 Ωm - 7 Ωm), sandstone-1 (10 Ωm – 33 Ωm), and sandstone-2 (14 Ωm - 17 Ωm). Integrated analysis resulted 2 potential location for drilling with coordinates for location 1 UTM 49M 664327mT, 9082526mU, 346 mdpl and location 2 UTM 49M 664333mT, 9082750mU, 349 mdpl. (author)