Evaluation of Sea water Intrusion in Freshwater Aquifers in a Lagoon Coast: A Case Study of the University of Lagos Lagoon, Akoka, Nigeria.
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New York Science Journal
ABSTRACT: A geophysical technique has been employed to investigate seawater intrusion into freshwater aquifers in the coastal environment of the Lagos lagoon at the University of Lagos campus, Akoka, south-western Nigeria. Electrical resistivity method employing the Schlumberger array was used to acquire data for six vertical electrical soundings to investigate the vertical extent of seawater intrusion. The study revealed that the subsurface in contact with the lagoon was invaded by saline oceanic seawater. The Schlumberger electrode array which utilized current electrode half spacing from 1m to 500m was used to acquire both resistivity and induced polarization data in the proximity of the Lagos lagoon. Typical curve types reported for coastal areas such as the KQ, KQQ, and HKQ were observed in the investigated area and 4-6 geoelectric layers were delineated at an average depth of 71m. The subsurface lithology comprised of fine through medium grained sand to coarse sand intercalated in most cases with sandy clay and clayey sand. The resistivity of the intruded saline water was found to range between 1.8-37.2Ωm at a depth interval of 0.7-79m and the thickness of saline layers was found to be greater in the proximity of the coastline. The result of the investigation revealed that even under non-pumping conditions, the study area suffers from acute saline water intrusion and could be aggravated if there is groundwater abstraction. Ways to check the seawater intrusion problem through artificial recharge have been proposed in the study.
Geoelectric sections , resistivity , seawater intrusion
Oyedele, K. F., & Momoh, E. I. (2009). Evaluation of Sea water intrusion in freshwater aquifers in a Lagoon Coast: a case study of the University of Lagos Lagoon, Akoka, Nigeria. New York Science Journal, 2(3), 32-42.