A Multi-criteria Decision using the Analytical Hierarchy Process (AHP) for Delineation of Groundwater Potential Zones in Part of the Obudu-Massif, Nigeria

Abstract

Groundwater occurrence in crystalline basement terrains is strongly controlled by lithology, structural features, topography, and climatic conditions. This study evaluated groundwater potential zones (GWPZ) in parts of the Obudu Massif, Southeastern Nigeria, Using an integrated Geographic Information System (GIS) and Analytical Hierarchy Process (AHP) approach. Eight groundwater conditioning factors, namely lithology, lineament density, drainage density, precipitation, elevation, slope, aspect, and curvature, were analyzed and weighted through pairwise comparison with the AHP framework. The resulting consistency ratio (CR) of 0.071 indicated acceptable consistency in the weighting process. The analysis revealed that geology/lithology (42.6%) and lineament density (18.6%) exert the greatest influence on groundwater occurrence, followed by drainage density (12.5%) and slope (10.5%). The groundwater potential map produced, delineated the study area into three classes: low high and very high GWPZs. Raster pixel interpretation showed that high GWPZ cover approximately 119 km² (49.3%) of the study area, while very high GWPZ occupy about 30km² (12.3%). Low GWPZ account for 92 km² (38.4%). Areas with very high groundwater potential are mainly concentrated within the central-southern and southeastern portions of the study area, where favorable lithologic and structural conditions enhance groundwater recharge and storage. A strong positive agreement between intermediate-to-high transmissivity values obtained from pumping-test data and the mapped high-to-very-high groundwater potential zones confirmed the reliability of the model. The high to very high GWPZs were considered indicative of the model accuracy. The study demonstrates that the integration of GIS, remote sensing, and AHP provides a reliable and cost-effective approach for groundwater exploration, borehole siting, and sustainable groundwater resource management in crystalline basement terrains.