Determination of Aquifer Properties and Groundwater Vulnerability Mapping Using Geoelectric Method in Yenagoa City and Its Environs in Bayelsa State, South South Nigeria

Abstract

Nineteen Schlumberger vertical electrical soundings (VES) were carried out within and around Yenagoa city, South South Nigeria, using a maximum current electrode separation ranging between 300 - 400 m. The objectives of the study were 1) to evaluate the possibility of mapping Quaternary sediments to infer the geological structure from the electrical interpretation and identify formations that may hold fresh water with low concentration of conducting minerals such as iron 2) to evaluate the vulnerability of the aquifer in the study area. The interpretation of the data collected was by computer assisted iterative interpretation using 1-D inversion technique software (1X1D, Interpex, USA). The results of the interpretation revealed four distinct geoelectric layers. Sounding curve types obtained in the area are mostly of the form <i>ρ</i><sub>1</sub> > <i>ρ</i><sub>2</sub> < <i>ρ</i><sub>3</sub> < <i>ρ</i><sub>4</sub> (where <i>ρ</i> is the density) but fresh water lenses with low concentration of conducting minerals such as iron were obtained only in locations that exhibit <i>ρ</i><sub>1</sub> > <i>ρ</i><sub>2</sub> < <i>ρ</i><sub>3</sub> < <i>ρ</i><sub>4</sub> curve types. Depth to the aquifer ranges from 4.5 m in the vicinity of VES 05 to 27.0 m at the vicinity of VES 14. The resistivity of the aquiferous horizon varies between 60 - 2868 Ωm. High transverse resistance values obtained were associated with zones of high transmissivity which agrees with the geology of the Benin Formation (Coastal Plain sands) consisting of fine-medium-coarse sands. The aquifer vulnerability map illustrates the impermeability of the overburden clay layer. Values of >0.5 mhos indicate good protective capacity, while values <0.3 mhos indicate vulnerable zones with probable risk of contamination

Assessment of Groundwater Potential and Aquifer Characteristics in the Vicinity of Igun, Eku and Oria in Delta State, Nigeria

“…The fourth layer aquifer is inferred from the results to be more prolific than the third layer aquifer. The resistivity of the fourth layer ranges between 2212 and 4260 Ωm while the depth to the aquifer layer is between 24.7 and 31.9 m. The result of the geoelectric interpretation also shows that the thickness of the aquitard ranged between 3.1 and 6.3 m. This is sufficiently thick to keep the groundwater safe from contamination [14].…”

Site-Specific Aquifer Characterization and Identification of Potential Groundwater Areas in Pakistan

“…Similarly, toll bar buttons are provided for the most used menu commands, including new sounding, open and import data, save, display selection, zoom status, un-zoom, edit data, forward, equivalence and inverse calculations, and determination of layered and smooth models. The methods of iteration in the software were performed until the fitting error between the measured and the predicted field data became minimum and constant [14,18]. Two boreholes were drilled to a depth of 80 m below the ground surface to verify the VES results [15].…”

“…For a homogeneous, isotropic, and horizontal layer, LC (mho) is expressed as LC i = h i /AR i and TR is expressed as TR i = AR(h i ), where h i is the thickness in meters of the ith layer, and AR i the apparent resistivity in Ohm-meters of the ith layer. Similarly, the LC has been used to evaluate the APC of the aquifer overburden [18]. The total dissolved solids (TDS) were also determined from water chemical analysis, and the relationship between TDS and AR was developed to examine groundwater quality.…”

“…So, it is suspected that leachate goes down through the soil and is mixed with groundwater because there is no proper mechanism to collect leachate and protect the aquifer. The need, therefore, arises to evaluate the aquifer protective capacity (APC, which is defined as the capacity of the aquifer material to underline and filter percolating surface polluted water into the aquifer) of the overburden material in the area in order to establish the level of safety of the hydrogeologic system [17][18][19].…”

Assessment of Economically Accessible Groundwater Reserve and Its Protective Capacity in Eastern Obolo Local Government Area of Akwa Ibom State, Nigeria, Using Electrical Resistivity Method

“…Recently, the activities of criminals who are involved in illegal pipeline vandalism and crude oil theft and refining have compounded the environmental problems in the Niger Delta region. The quality of the groundwater resources in many parts of the region is gradually being degraded [5]. There is urgent need to understand the extent of natural protection, the distributions of the economically safe aquifer repository, and possibly the pollutant flow path in order to design appropriate mitigation, remediation, and protection strategies especially now that such plans are in the drawing board by governmental, environmental, and other international partners.…”