Groundwater potential mapping in hard rock terrain using remote sensing, geospatial and aeromagnetic data

Abstract

• Geospatial techniques applied in integrated water resources management. • Remote sensing data reveal groundwater recharge zones. • Aeromagnetic data have a higher depth of investigation than remote sensing data. • Integrating remote sensing and geophysical data can surpass depth probing methods. The need for water security in different regions of the world has led to the deployment of remote sensing (RS) and geographic information systems (GIS) as decision support tools with geophysical methods. In this study, the remote sensing, geospatial and aeromagnetic data were integrated for mapping the groundwater potential at the University of Ilorin, Nigeria in West Africa. Several remote sensing and geospatial datasets (geomorphology, lineament density, slope, rainfall, land use/land cover, soil type and drainage density) were enhanced, weighted, prioritised and ranked using the analytical hierarchy process (AHP) technique. Subsequently, the thematic datasets were integrated into a GIS platform to produce a groundwater potentiality zonation (GWPZ) map. Visualisation of the corrected aeromagnetic data was improved by using some image enhancement techniques (filters) to produce the magnetic anomaly maps that revealed gross and subtle subsurface features. Multiple validation of the GWPZ map was achieved using the magnetic anomalies maps, borehole groundwater potential indices (GWPI) and the receiver operating characteristic (ROC) curves. The GWPZ map generated was classified into three groundwater potential classes with different spatial distributions. These include moderate (60.6%), high (5.9%), and low (33.5%). The magnetic anomalies maps agreed well with the remotely sensed models through surface-subsurface lineaments superposition. The area under curve (AUC) of the ROC showed that the predictive rate of the GWPZ model was 0.73. This value suggested that the model satisfactorily predicted the groundwater potential of the study area. Thus, this present study demonstrated the relevance of geospatial and geophysical techniques for regional groundwater potential mapping at the assessment phase of integrated water resources management towards providing a better understanding of the hydrogeology for easy decision-making and better groundwater management.