Groundwater is among the most important resources of water supply of the worldwide population. The objective of this research is to select the most suitable drilling location of new groundwater wells, with a decision-making tool using geographic information system (GIS). The optimum location was evaluated based on the hydro-geoelectrical parameter derived from vertical electrical sounding (VES) including longitudinal conductance, aquifer thickness, aquifer resistivity, transmissivity, formation factor, and porosity. The analysis of the VES data revealed that the porosity values range from 1.8 to 21%, the formation factor values vary between 0.0355 and 0.14, the transmissivity values range from 3.4 to 6 m²/day, the longitudinal conductance values vary from 3 to 4.6 Ω⁻¹, the aquifer thickness values range from 4.1 to 8.5 m, the aquifer resistivity varies between 0.7 and 40 Ω m. Hydro-geoelectrical data were integrated into GIS to precisely determine the best location for groundwater wells. Fuzzy liner membership was used to standardize the criteria layers; then, these layers were combined using fuzzy gamma overlay to produce the suitability map. The study area was classified into four classes: excluded, low suitability, moderate suitability, and high suitability. It is recommended that this method should be adopted by different governmental agencies involved in water resources management in Nigeria.

This study assesses groundwater vulnerability in Owerri, Nigeria, using Vertical Electrical Sounding (VES) and Geographic Information System (GIS)-based DRASTIC modeling. The research methodology includes literature review, field survey, geological feature mapping, hydrogeological assessment, geo-electrical sounding, and data interpretation. Owerri, a rapidly developing city with flat topography and a growing population, uses the DRASTIC model to construct a groundwater vulnerability map. The model evaluates the risk of groundwater contamination using seven critical criteria, including depth to water table, net recharge, aquifer media, soil media, topography, vadose zone impact, and hydraulic conductivity. Each parameter was given a weight and rating, and the DRASTIC Index (DI) was calculated by summing the products of the weights and ratings for each factor. The results of the vulnerability assessment indicated that approximately 49% of the study area falls into the high vulnerability category, around 45% is classified as moderate vulnerability, and the remaining 6% is labeled as low vulnerability. The study reveals moderate to high vulnerability zones in Owerri, Nigeria, due to factors like lower slope terrain, permeable aquifer media, and vadose zone impact. The use of VES and GIS-based DRASTIC mapping techniques provides insights into groundwater vulnerability, aiding in sustainable resource management and environmental protection. The findings emphasize the importance of understanding potential risks and the need for effective management strategies to safeguard clean water supplies. Further research and mitigation efforts should focus on highly vulnerable areas.