Aeromagnetic and Resistivity Tomography Technique for Investigating Leakage Paths in Apodu Dam, Ilorin Sheet 201, Southwestern Nigeria

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Alhikmah University


The aeromagnetic and electrical resistivity tomography technique was used to evaluate the foundation conditions and stability of the Apodu earth dam located around Malete, Ilorin Sheet 201, Southwestern Nigeria. The Aeromagnetic data set was interpreted to identify dykes, lineaments, and magnetic sources controlling subsurface geology. The extracted lineament structures were employed to examine features controlling the distribution of surface and subsurface hydraulic substances cum stability of dam slope. Magnetic lineaments' length and parallelism in some areas suggested installation under a tensional stress field along pre-existing zones of weakness.Magnetic susceptibilities are not uniform in the area and were categorized viz: high, moderate, and low. The magnetic intensity range at Apodu dam is -644.19 to 285.40 nT. The northeastern part of the study area where the Apodu dam is located shows little or no sign of faulting and appears to be more stable structurally. Characterization of the Apodu dam subsurface for seepage appraisal using electrical resistivity tomography technique revealed that the dam is well compacted at the surface but with observed low resistivity values indicative of possible occurrences of weakness zones that are water-bearing in some areas of the dam embarkment body at depths of around 8m and 25m. These observed low resistivity zones indicating a water-bearing weakness zone were connected in RTM1 and RTM2, and a possible water pathway was established. This water pathway is indicative of a possible seepage pathway and adequate measures are expected to be made to arrest the situation. In conclusion, Apodu dam is situated in a geologically stable environment as deduced from the aeromagnetic study but its earth embarkment is suspected to possess areas with possible seepage zones as obtained from the electrical resistivity techniques of investigations. There is therefore a need to quickly remedy the dam earth embankment to ensure the longevity of the dam and avert possible failure.



Aeromagnetic, Resistivity tomography, Geologic structure, Dam Seepage