Indra Arifianto (1), Kartika Palupi Savitri (1), Muhammad Rachmat Fadhil Priana (1) and Agung Setianto (1)
(1)Department of Geological Enginnering, Universitas Gadjah Mada.
The research area is located in Camba-Camba Village, Batang, Jeneponto, South Sulawesi Province, Indonesia. This area is included in the the Indonesian Government ‘development acceleration program for underdeveloped regions’. This research area shows a flow ridge volcanic morphology consisting of volcanic breccia, tuffaceous sand, and laharic clay deposit from Lompobatang Volcanic Formation. The geological condition leads to a scarcity of groundwater in the area, which makes looking for a great groundwater source is challenging. On the other hand, such a groundwater source is needed to fulfil the water demands of plantation and rice field irrigation, particularly in the dry season. The geoelectric or resistivity method was used in this study to determine the location and depth of groundwater aquifers. The resistivity method used was the vertical electrical sounding (VES) “Schlumberger” method which aims to identify the variation of subsurface rocks resistivity value against depth. Through an inversion resistivity modeling, the true resistivity value in this area ranges from 0.87 to 6117 Ωm. There are five groups of subsurface rocks that could be identified based on these values, namely claystone aquiclude, shaly sand aquitard, tuffaceous sandstone aquifer, volcanic breccia aquitard-aquifuge, and lava aquifuge. Each group, respectively, showed a resistivity value of 0.87-10.63 Ωm, 12.74-22.91 Ωm, 18.83-58.25 Ωm, 62.46-159.5 Ωm, and 414-6117 Ωm. Based on the results of the correlation and modelling of these five groups, a drilling site location was set near the JPT 02 resistivity measurement point, where the model showed an aquifer at the depth of 50 meter. The presence of this aquifer was confirmed by the drilling.
KEY WORDS: Resistivity method, groundwater exploration, volcanic morphology, tuffaceous sandstone
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