Mapping of aquifer geometry using resistivity geoelectrical methods in Bukit Intan sub-district

Abstract Pangkalpinang City lies beyond any delineated groundwater basin and frequently experiences water shortages during the dry season due to limited recharge and storage capacity. This study was conducted to map aquifer geometry and characterize the hydrological framework within the granitic terrain of Bukit Intan Sub-district using the geoelectrical resistivity method. Three two-dimensional resistivity profiles, 150–200 m in length with 20 m electrode spacing, were acquired using a dipole–dipole array configuration. The data were inverted through a smoothness-constrained least-squares algorithm to obtain subsurface resistivity models. The results delineate three principal layers a near-surface unsaturated zone (900–2000 Ω·m) consisting of sandy–clayey materials, a saturated zone (170–1900 Ω·m) representing the main aquifer hosted in weathered granite and alluvial deposits and a high-resistivity basement (>2000 Ω·m) corresponding to compact granite acting as an aquitard. The aquifer was identified at depths of 5–20 m and exhibits lateral continuity consistent with regional borehole data. These findings provide essential insights for sustainable groundwater utilization, recharge-zone protection, and environmentally resilient water management in non-basin granitic terrains of Pangkalpinang.