Remote Sensing and GIS-Based Groundwater Potential-Zone Mapping in Imo State, Southeastern Nigeria

Groundwater is an important source of water for domestic, agricultural and economic activities, yet its spatial occurrence is controlled by interacting geological, hydrological, terrain, soil and land-use factors. This study delineated groundwater potential zones in Imo State, southeastern Nigeria, using an integrated remote sensing and Geographic Information System (GIS) approach. Landsat 8 Operational Land Imager/Thermal Infrared Sensor (OLI/TIRS), Shuttle Radar Topography Mission (SRTM) digital elevation data, rainfall, soil, geological, drainage-density and lineament datasets were integrated to characterize factors controlling groundwater occurrence. The thematic layers were reclassified according to their relative groundwater potential, weighted using the Analytical Hierarchy Process (AHP), and integrated through GIS-based weighted-overlay analysis. Overlay analysis was also used to examine relationships between groundwater potential, soil characteristics and terrain slope, while logistic regression was applied to investigate the association between land-use/land-cover (LULC) and groundwater occurrence. The resulting groundwater-potential map classified the study area into very-low, low, moderate, high and very-high potential zones. The moderate-potential class constituted the largest reported proportion of the study area (59.6%), followed by low (20.2%) and high (18.6%) potential zones. The reported validation produced an overall mapping accuracy of 97.4%, with class-specific accuracies ranging from 91.7% to 99.3%. Sandy-loam soils and areas with relatively gentle slopes were associated with greater groundwater potential, whereas steeper terrain was generally associated with lower potential. The LULC analysis indicated greater groundwater occurrence in vegetated areas than in built-up areas. The study demonstrates the usefulness of integrating remote sensing, GIS and statistical techniques for regional groundwater-potential assessment and provides a spatial basis for groundwater planning and management in Imo State.