Integrating GIS and multi-influencing factor technique for delineation of potential groundwater recharge zones in parts of Ilesha schist belt, southwestern Nigeria

In this study, the multi-influencing factor (MIF) technique was implemented through geographical information system to delineate potential zones of groundwater recharge. The hydrogeological factors influencing groundwater recharge namely lineament, drainage, lithology, slope, land use, rainfall and soil were classified and integrated based on weight derived through the MIF technique. Integration of these factors enabled the generation of potential groundwater recharge zone map which was classified into four categories namely high, moderate, low and very low occupying areas of 214.9 km2 (14.6%), 599.2 km2 (40.8%), 502.3 km2 (34.2%), and 152.4 km2 (10.4%), respectively. A total of 55.43% of the study area was found to have moderate to high recharge potential. Areas of high recharge potential lies majorly within the quartzite lithology and parts of undifferentiated migmatite-gneiss bordering the highly fractured quartzite. Estimation of the infiltration rate based on the potential recharge zone map classes revealed that approximately 27% of the precipitated rainfall volume is probably infiltrated into the subsurface; however, the actual percentage reaching the underlying aquifer is expected to be lower due to losses through subsurface flow intercepting river channels. Yields of wells within the study area revealed that recharge has significant influence on well yields. Wells within the zones of high to moderate recharge potential were found to have substantial yields while the well located within the zone of low recharge potentiality was found to have negligible yield. Negligible yield is also expected in areas with very low recharge potential. The result portrays the potential groundwater recharge zones in the study area and is found to be helpful in better planning and management of groundwater resources to maintain a proper balance between the groundwater quantity and its exploitation.