Chemosphere 316 (2023) 137305 Available online 18 November 2022 0045-6535/© 2022 Elsevier Ltd. All rights reserved. Integrated hydrogeophysical and GIS based demarcation of groundwater potential and vulnerability zones in a hard rock and sedimentary terrain of Southern India K. Sankar a , D. Karunanidhi b, * , K. Kalaivanan c , T. Subramani d , D. Shanthi e , P. Balamurugan f a Department of Industrial and Earth Sciences, Tamil University, Thanjavur 613010, India b Department of Civil Engineering, Sri Shakthi Institute of Engineering and Technology (Autonomous), Coimbatore 641062, India c Department of Geology, Bharathidasan University Triuchirappalli 620023, India d Department of Geology, College of Engineering, Guindy, Anna University, Chennai 600025, India e Department of Geography, Government Arts College, Triuchirappalli 620022, India f Department of Community Medicine, Saveetha Medical College, SIMATS, Chennai 602105, India HIGHLIGHTS G R A P H I C A L ABSTRACT • IPI2Win was used for curve matching to evaluate VES data obtained from 95 locations. • Spatial variations of thickness of top soil, weathered zone and fractured zone were plotted using GIS. • Thickness of weathered zone varied from <10 m to >38 m, which played a major role in groundwater occurrence. • Groundwater potential zones were demarcated using hydrogeophysical investigations. A R T I C L E INFO Keywords: Hydrogeophysics Vertical Electrical Sounding (VES) GIS Aquifer thickness Aquifer anisotropy Groundwater potential Southern India ABSTRACT This research has identifed the groundwater potential and vulnerability zones in Tiruchirappalli district of Tamil Nadu, India. The Schlumberger electrode array has been used to conduct vertical electrical sounding (VES) at 95 sites with a maximum electrode spacing of 150 m. The study area comprises of hard rock and sedimentary formations. Geographical Information System (GIS) has been used to integrate the geoelectrical data and to prepare spatial variation maps for various parameters. Finally, groundwater potential and vulnerability zones have been demarcated, and these outputs have been validated using water level and nitrate data, respectively. The Dar-Zarrouk parameters such as longitudinal conductance (S), transverse unit resistance (T), and aquifer anisotropy (λ) have been used along with the spatial variation of resistivity and aquifer thickness to fnd out groundwater potential areas with the support of GIS. The thickness of topsoil, weathered zone and fractured zone are not uniform in the research area. Top soil plus weathered zone acts as a water table (phreatic) aquifer, which extends up to 38 m from the surface. Fractured zone extends up to 45 m, which acts as a kind of confned/semi- confned aquifer. Open and bore wells have been constructed to tap groundwater from the unconfned (water table) and confned/semi-confned aquifers, respectively. High to very high groundwater potential areas are associated with low resistivity, high thickness, low longitudinal conductance, high transverse unit resistance and * Correspondence to: Department Civil Engineering, Sri Shakthi Institute of Engineering and Technology (Autonomous), Coimbatore 641062, India. E-mail address: karunasamygis@gmail.com (D. Karunanidhi). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere https://doi.org/10.1016/j.chemosphere.2022.137305 Received 7 July 2022; Received in revised form 19 October 2022; Accepted 17 November 2022