ONE-DIMENSIONAL GEOELECTRICAL INVESTIGATION OF GROUNDWATER IN TAPUNOPAKA VILLAGE

Tapunopaka village is located in the Lasolo Kepulauan sub-district, North Konawe regency. It is surrounded by Bahubulu island and Labengke island in the eastern part. Geologically, the area is composed of alluvium sedimentation which has a good potential to be an aquifer. Furthermore, the hydrogeological map shows that the area has a good potential to be an aquifer with moderate transmissivity below 5 liter/second. However, based on the field investigation the water spring in Bahubulu island is the main water resources for Tapunopaka’s villagers. No transmissivity water system has been found in the Tapunopaka as well. In addition, based on the drought risk map in Southern Sulawesi Province which was issued by the National Disaster Management Authority (BNPB) 2015, the Tapunopaka village has a moderate risk potential. As a result, to provide another water resources in the Tapunopaka village and to anticipate the drought disaster in the future, a geophysical investigation has been conducted in the area. Geopysical investigation of Tapunopaka village, Lasolo Kepulauan sub-district, North Konawe regency was undertaken to explore the potential of ground water resources. The Vertical Electrical Sounding (VES) was chosen as a method to determine the groundwater resources. There was four locations were conducted around the Tapunopaka Village by using the Schlumberger configuration. The VES data were subjected to an iteration software (IP2win) with the maximum RMS error below 10% compared to the mathematical appraisement. The result shows that Tapunopaka composed of top soil, sand and clay as an alluvial sediment, and weathered ultramafic rock. The result of quantitative interpretation shows that sand and the weathered ultramafic rock have been identified as an aquifer, while clay as an aquitard. Even though sand can be an aquifer, but the target aquifer in this study is the weathered ultramafic rock. The weathered ultramafic rock is the thicker layer in the VES. More than 100 meter of thickness has been interpreted during the study. Based on the low resistivity values, layer thickness, and overburden thickness, TPK-4 has the brightest potential for future groundwater exploration and development. The TPK-4 composed of 109.13 meter thickness of weathered layer with 13.81 meter of thickness in clay layer as an aquitard. Furthermore, by using the Darcy’s law the groundwater in the weathered layer has a potential debit around 7.07 liter/second. Keywords : Tapunopaka, Groundwater, Geoelectric, VES