The Delineation of Groundwater Aquifer Systems Using Vertical Electrical Sounding (VES) in Sesela Village, West Lombok, Indonesia

Abstract

The expansion of residential areas in Sesela Village, West Lombok, has led to increased groundwater demand, while subsurface hydrogeological information remains limited. This study aims to delineate aquifer systems and characterize subsurface conditions to support preliminary groundwater assessment in the study area. The investigation was conducted using the resistivity method through Vertical Electrical Sounding (VES) with a Schlumberger configuration. Two VES points, spaced approximately 30 m apart, were acquired and interpreted using one-dimensional inversion to obtain resistivity values and layer thicknesses. The results from both VES points indicate a consistent subsurface structure consisting of seven layers. The interpreted lithology include topsoil, sand and gravel, volcanic breccia, lapilli tuff, and sandy tuff. Based on resistivity characteristics, three aquifer systems were identified. A shallow unconfined aquifer occurs at depths of 1.5–5 m, with resistivity values ranging from 10 to 25.4 Ωm, associated with sand and gravel deposits. An intermediate semi-confined aquifer is identified at depths of 9–26 m, with resistivity values between 23 and 29.3 Ωm, corresponding to lapilli tuff. A deeper confined aquifer is observed at depths of 57–116 m, with resistivity values ranging from 18.9 to 22.5 Ωm, interpreted as sandy tuff. These aquifer layers are separated by volcanic breccia layers characterized by relatively high resistivity values (131–671 Ωm), which act as aquitards. The similarity of resistivity patterns between the two VES points suggests relatively consistent vertical layering, although minor variations in depth are observed. The results provide preliminary information on aquifer distribution and subsurface conditions, which may serve as a basis for further hydrogeological investigation and groundwater resource assessment in Sesela Village.