Integrated hydrogeophysical assessment of groundwater potential in the Ogun drainage basin, Nigeria

摘要

This study explores possible groundwater areas in the Ogun drainage basin in Ogun State, Nigeria, using the Vertical Electrical Sounding VES system for remote sensing and GIS. Thematic maps are built as geodatabase or GIS layers of lineament density, lithology, land use and land cover, drainage and slopes. Each layer is given weights based on a pair comparison of considerable factors in the retention, storage and transmission of groundwater. Potentials are created through the analysis process hierarchy (AHP) in a GIS environment that includes five thematic maps with factors that result in groundwater occurrence and movement using weighted overlay. We assigned weightages of factors influencing groundwater prospects such that lithology had the highest (43%) followed by lineament density (33%). Slope weighed (13%) and drainage density (7%). The least groundwater contributor in the study area, {is the} land use/land cover was assigned 4%. The AHP consistency ratio CR was calculated to be 0.04 for this analysis which is less than the threshold consistency value of 0.10. The result of the study showed that high groundwater potential occupies 3818.57km~2 (21%) and low potential areas constitute 1022.50 km2 (6%) of the study area including. The moderate and very low potentials occupy the highest coverage constitute about 5530.63 km2 (31%) and 7725.37 km2 (42%) respectively. Validation of the aquifers from the VES shows that the GIS analysis map for groundwater potential corresponds to field results. However, it is suggested to add more detailed VES data, well data/ pumping tests into the GPZ map for accurate validation.