Assessing the Protective Capacity of Aquifers Using Very-Low-Frequency Electromagnetic Survey

Abstract

The protective capacity of aquifers is a prerequisite for groundwater quality in areas prone to contamination from the ground surface. Aquifers without protective layers are more susceptible to contaminations from point and non-point sources. The protective capacity of an aquifer significantly correlates with the thickness of clay and organic materials that mantled it. To assess aquifer protective capacity, electrical conductivity property of saturated clay was determined from filtered imaginary and real components of Very Low-Frequency Electromagnetic (VLF-EM). The filtered real components against distance and current density pseudo-section produced from real components were concomitantly used for interpretation. Clays capping aquifers were delineated from those without capping from low and high values of filtered imaginary and real components and current density pseudo-section. The distribution of clay laterally across the area indicates that aquifers are poorly protected and susceptible to contaminations from a point and non-point sources. The apparent agreement between inferred geology from VLF-EM interpretation, borehole data and resistivity data underscores the efficacy of VLF-EM as an important tool that can be used or combined with other geophysical methods and borehole information/data for assessment of the protective capacity of the aquifer.

A Preliminary Study of Groundwater Conditions in a Transitional Environment of Niger Delta using Direct – Current Soundings

“…Spatial development of the aquifer architecture of facies resistivity revealed from this investigation follows a trend of mostly sand with little clay in the south to sand with abundant of clayey facies in the north near the Forcados River. This is typical of lithological succession revealed by others [10,[22][23][24]. The iso-resistivity map of Burutu at different depths, as shown in Fig.…”

Lithofacies Identification and Multivariate Analysis of Groundwater Chemistry in Coastal Aquifers in Koko Area of the Western Niger Delta

“…Aquifers mantled by impermeable geological materials tend to retard migration of contaminants and are less vulnerable to contamination compared to those with underlying permeable materials. Thus the quality of groundwater in an aquifer is essentially controlled by the lithology above and within it [5].…”

“…The objectives of study were (1) to identify the subsurface lithofacies of the materials that constitute aquifer and aquicludes, (2) to determine the groundwater quality from the alluvial plains and to assign factors shaping their quality, (3) to use the dimension reduction technique associated with multivariate analysis to explain similarity among groundwater parameters, (4) to establish factors controlling groundwater quality and evolution, and (5) to classify groundwater into group and identify factors that influence them from cluster analysis. The implication of the study is to ensure the availability of accurate and concise groundwater quality data relevant to policy developers and water managers for the effective and robust management of groundwater resources for sustainable development.…”

The use of very low-frequency electromagnetic survey in the mapping of groundwater condition in oporoza-gbamaratu area of the Niger Delta

“…In Utah County, the USA, VLF integration with electrical resistivity was used for the delineation of shallow alluvial aquifer contaminated by hydrocarbon (Alvin et al 1997). Ohwoghere-Asuma et al (2018) and Aizebeokhai and Oyeyemi (2015); have at different places demonstrated the effectiveness of same methodology in aquifer vulnerability study and delineation of high resistivity layers in sedimentary terrains in the Niger Delta and southwestern Nigeria, respectively.…”

“…Like electrical resistivity technique, the very low-frequency electromagnetic (VLF-EM) is sensitive to ground water quality (Sharma and Baranwal 2005) and conductive geological materials in the subsurface (Ohwoghere-Asuma et al 2018). It is the easiest to use of all known electromagnetic methods for subsurface exploration.…”