Al-Hikmah University Central Journal
AEROMAGNETIC AND RESISTIVITY TOMOGRAPHY TECHNIQUE FOR INVESTIGATING LEAKAGE PATHS IN APODU DAM, ILORIN SHEET 201, SOUTHWESTERN NIGERIA
Abstract
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 seepages 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.
