Geophysical Assessment for Characterising Leakages from Asa Dam, Nigeria

Abstract

Aeromagnetic and Electrical resistivity tomography technique were used to evaluate the foundation conditions and stability of Asa earth dam located in Ilorin, The Aeromagnetic data set was interpreted to identify dykes, lineaments, and magnetic sources that is controlling the subsurface geology. The extracted lineament structures were employed to examine features that are controlling the distribution of surface and subsurface hydraulic substances which affects the stability of dam. the nature of the magnetic lineaments in some parts of the area suggests rock emplacement under a tensional stress field. Magnetic susceptibilities area not uniform in the area and were categorized viz: high, moderate and low. The magnetic intensity range at Asa dam is 126.56 to -20.90 nT. The northwestern part of the Asa dam area shows little or no sign of faulting and appears to be more stable structurally than the other part of the study area. Characterization of Asa dam earth embarkments for seepage appraisal using resistivity tomography technique revealed that the Asa dam is well compacted with no sign of any seepage. In conclusion, the Asa dam is situated in a geologically stable environment as deduced from the aeromagnetic study, while the earth embarkments are well compacted with no sign of seepage as obtained from the electrical resistivity tomography technique of investigations.