Geophysical investigation of saline water intrusion into freshwater aquifers: A case study of Oniru, Lagos State
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Date
2010
Authors
Adeoti, L
Alile, O.M
Uchegbulam, O
Journal Title
Journal ISSN
Volume Title
Publisher
Scientific Research and Essays
Abstract
A total of five electrical imaging lines were measured using the wenner configuration. And a total of
twelve VES was carried out within the area of investigation. The lines were aligned almost in a linearly
NS azimuths, perpendicular to the ocean. The results were presented as profiles, multi-profiles, maps,
pseudo sections and inverted sections. Interpretations of these results involve both qualitative and
quantitative deductions from 1D and 2D geoelectric models. WingLink software was utilized for plotting,
filtering, modeling and iterations of the resistivity data. From the quantitative interpretation and nearby
well log data five distinct layers were identified. The layers are dry and unconsolidated sand, clayey
sand, saline sand, saline clay and freshwater sand. The resistivity of the topsoil varies from 3259.59
Ohm-m on VES 2 - 67.04 Ohm-m on VES 12. The resistivity of the freshwater sand varies from 1649.76
Ohm-m on VES 6 - 158.28 Ohm-m on VES 10. The resistivity of the saline layer (saline sand/clay) varies
from 2.06 Ohm-m on VES 12 - 39.88 Ohm-m on VES 3. The depth to saline/freshwater interface varies
from 12.97 m on VES 8 - 63.01 m on VES 5. The quality of groundwater varies from poor polluted saline
water saturated sand/clay through intermediate water quality clayey sand/sand to freshwater sand. The
interpreted results show saline water plumes where they occur in different part of the area investigated.
The 1D and 2D results correlate to a very high degree indicating saline water intrusion between depth
interval of 13 and 64 m in the study area. Two major freshwater aquifers (shallow < 6 m and deep > 60
m) where delineated with most of them occurring unprotected. The results showed the effectiveness
and usefulness of electrical resistivity and induced polarization method in mapping saline water
intrusion problem in coastal areas.
Description
Keywords
Geophysical investigation , saline water , aquifers , coastal terrain
Citation
Adeoti, L., Alile, O. M., & Uchegbulam, O. (2010). Geophysical investigation of saline water intrusion into freshwater aquifers: A case study of Oniru, Lagos State. Scientific Research and Essays, 5(3), 248-259.