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Delineation of Groundwater Potential Zones in Oyo State, Nigeria using Multi Criteria (MIF and AHP) and Hydro Geophysics

Oluwagbemi Emmanuel, Sumu-Epuh, Emeka Eusebius, Joshua Bassett, Famiwaye Olushola Victor, Daramola Olagoke Emmanuel, Yvonne Orji, Joseph Michael

This study was carried out to delineate groundwater potential zones in Oyo state, southwestern Nigeria using an integrated approach of remote sensing, Geographical Information System (GIS) and Hydrogeophysics. Seven (7) thematic layers of land cover, drainage density, lineament density, soil, geology, slope, and rainfall were processed and prepared using satellite imageries and geographical information system techniques. Two different multi-criteria analysis techniques: Multi Influencing Factor (MIF) and Analytic Hierarchy Process (AHP) were employed in assigning weights to each thematic layer and internal features. The Integration of the layers was done using the weighted overlay analysis tool in ArcGIS software to develop groundwater potential zones. In the Hydrogeophysics, the Groundwater Potential Conducting Factors (GPCFs) were evaluated using the Vertical Electrical Sound (VES) data. The results of the MIF and AHP were further integrated into one map to obtain a ptimum result. Five classes were obtaining with the percentage distribution as: very high (1%), high (29%), moderate (62%), low (8%) and very low (0.01%). The longitudinal conductance values ranges from 0.04 Ω-1 to 0.12 Ω-1 (low conductance) and in the region with higher longitudinal conductance its values range from 0.12 Ω-1 to 0.24 Ω-1. Most of the values of the reflection coefficient of the study area are low (<0.8) signifying a good aquiferous zone. The ROC validation technique reveals that the AHP method has (AUC: 0.65) while the MIF and the integrated groundwater potentiality maps have (AUC: 0.60). This shows that the three approaches are significantly reliable for groundwater prediction.