Groundwater potential mapping in Ikorodu, Lagos State, Nigeria, using multi-criteria analysis and hydrogeophysics
The assessment of the potential groundwater recharge area is extremely important for water quality protection and proper management of ground water systems. The objective of this study was to evaluate systematic groundwater studies using the integration of remote sensing and geographic information systems (GIS) and hydrogeophysics as a tool to identify groundwater potential areas in Ikorodu, Lagos. In this study, various thematic maps (layers) derived from satellite image classification such as: Land use/ Land cover map, soil map, rainfall map, geological map, slope map derived from SRTM Digital Elevation Model, lineament density map obtained as a result if lineament analysis of the principal component of the image, were all integrated using the weighted overlay tool in the spatial analyst toolbox of ArcGIS 10.5. Ranks and weights of classes and sub-classes of the thematic layers were assigned based on their influences on groundwater occurrence. The vertical electrical sounding data obtained from the study area were used to validate the results of the groundwater potential map and also determine the areas with brackish water, saline water and freshwater and the most probable drillable depth for exploration. The results show that the groundwater potential zones of the study area could be classified into five zones with the following percentage for spatial distribution: “very high” potential zone (0.6%), “high” (4.2%), “moderate” (15.8%), “low” 71.7% and very low potential zone (7.7%). The South-Western region of Ikorodu, close to Oriwu has the highest concentration of groundwater. Imota is characterized with Moderate and Low ground water potentials. From the query results, the aquiferous layers were identified, their yield and potentials determined and the depths to which boreholes can be sunk for the drilling of fresh water were found to be between 20m and 120m respectively.
Keywords: Groundwater, Remote sensing, GIS, Hydrogeophysics.