Resistivity methods of aquifer mapping and pollution vulnerability assessment of a part of Imo River Basin of South-Eastern Nigeria (A case study of Mbaitoli Local Government Area of Imo State, Nigeria)
Date
2011
Authors
Journal Title
Journal ISSN
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Publisher
IDOSI Publications
Abstract
Aquifer mapping and pollution vulnerability assessment of a part of Imo River basin of South-eastern Nigeria has been carried out with the aim of addressing the underground water exploitation problems inherent in the area. The instruments used for the study include aerial photographs, satellite images, topographic and geologic map of the area. Geophysical investigations were carried out with the aid of terrameter 300 SAS employing vertical resistivity soundings. Eleven selected locations were sounded using Schulumberger array with maximum electrode separation of 900 meters. Result shows that the area has average lithology of eight (8) layers with underground water occurring between the fourth and fifth layers. The lithology is dominantly sand (about 90%) sandstone (about 2%) clay / shale (about 8%). Average depth to top of aquifer ranges from 100 to 228 meters. Depth to the base of aquifer ranges from 88m to 278m while the average aquifer thickness is 33.7m. Three aquifer systems exist in the area-confined, unconfined and semi-confined. Semi-confined aquifer is dominant, while unconfined aquifer is less common. The former offers natural protection against pollution of underground water by waste effluents while the later is prone to pollution. Average resistivity of the formations is relatively high indicating a formation likely to contain abundant conglomeritic and sandstone beds capable of promoting loss of circulation and difficulty in drilling bit penetration during underground water exploitation. Areas to the west are relatively shallow while the South (Egbeada) is very deep. There is an insignificant relationship between aquifer depth and elevation. This section of Imo River basin is promising for underground water development but requires caution since conglomeritic and sandstone traces can effect adversely underground water exploitation. Down the hole electric logging is necessary considering the aquifer depth. The problem of unprotected aquifer against environmental pollution should be noted and addressed.
Description
The article contains tables and figures
Keywords
Underground water, pollution, mapping, aquifer, Imo Sedimentary Basin, Nigeria, Department of Geosciences
Citation
Onunkwo, A. A., Uzoije, A. P. & Essien, A. G. (2011). Resistivity methods of aquifer mapping and pollution vulnerability assessment of a part of Imo River Basin of South-Eastern Nigeria (A case study of Mbaitoli Local Government Area of Imo State, Nigeria). American-Eurasian Journal of Agriculture & Environmental Science, 11(4), 482-489