Potential Groundwater Recharge Sites Mapping in a Typical Basement Terrain: a GIS Methodology Approach

The area of Akoko with a progressively increasing population and infrastructural development, underlain by rocks typified of a basement terrain, was subjected to the search for potential groundwater recharge sites, to meet the challenge of water demand in the future. Groundwater recharge indicators such as lithology, topography, geomorphology, lineament density, soil, rainfall, drainage density, and land use/land cover were employed for this study. Reclassified raster layers of these recharge indicators were generated from the acquired datasets. These indicators were then delineated, weighted, and classified on the basis of understanding of the local geology and hydrogeology of the study area using Saaty's approach (Saaty Eur J Oper Res 48:9-26, 1990). These indicators were integrated into a GIS environment to produce a potential groundwater recharge map for the Akoko area. Five classes of potential groundwater recharge (poor, fair, moderate, good, and very good, with the following area coverage of 446.42 km(2) (26%), 772.65 km(2) (45%), 291.89 km(2) (17%), 154.53 km(2) (9%), and 51.51 km(2) (3%), respectively, were delineated. The generated groundwater recharge map was validated with available borehole records that established a relationship between the groundwater recharge mapped areas and basement aquifers. The mapping of these recharge areas aided better understanding of the groundwater dynamics and proper water resource management for anticipated purposes in the Akoko area, and can be applied to any several basement terrains.