Electro‑geohydraulic estimation of shallow aquifer characteristics of Njaba and environs, Southeastern Nigeria
No Thumbnail Available
Date
2023
Journal Title
Journal ISSN
Volume Title
Publisher
Saudi Society for Geosciences and Springer Nature Switzerland
Abstract
2023
Abstract
The study investigated the use of electro-geophysical method as an alternative to pumping test method in the estimation of
geo-hydraulic characteristics of shallow aquifers in Njaba and environs, Southeastern Nigeria. This was done to ascertain
the aquifer potentials of the study area. Twenty-three geo-electric resistivity soundings were acquired using ABEM Terrameter
SAS-4000 and Schlumberger configuration with maximum half-current electrode spacing of 500 m. Geo-electric
layers were determined using FORTRAN 2D Resistivity Software. The results indicate an undulating topography, with
elevations ranging from 361 to 1336.9ft. Spread 5 m, 20 m, 50 m, 100 m, 150 m, 200 m, 250 m, 300 m, 400 m, and 500 m
were probed, which gave their corresponding resistivity values at different depth slices. Results showed a fairly increasingreducing-
increasing trend of resistivity values. An averaged high resistivity value can be traced to the presence of the sand
lithology of the Benin Formation in the region. Aquifer depth of 79.2 to 115 m was observed in the study area, showing a
semi-deep aquifer system. Aquifer thickness of 23.4 to 48.5 m was observed in the studies, with a mean value of 37.71 m.
Aquifer resistivity ranges from 28,700 to 990Ωm, indicating clean sand and sand with little clay admixtures, respectively.
Average longitudinal conductance (in Ω−1) of 0.00611693 and transverse resistance of 407,178.1739 was recorded in the
study area. Hydraulic conductivity (in m/day), as obtained from a new model, showed a high value of 27.90068 and a low
value of 0.0852, an indicator of fairly clean sand. Transmissivity (
m2/day), from a new model developed for the study area,
ranges from 430.0877 to 23.552. The storativity value ranges from 0.0001515 to 0.00113139, indicating a confined aquifer,
while average aquifer diffusivity of 1,398,057.749 was recorded. Altogether, aquifer vulnerability and hydro-geochemical
studies of the environment are recommended, to ascertain the protective capacity of the aquifer from the surface pollutants
and the quality of water in the study area, respectively.
Description
Keywords
Hydraulic conductivity · Transmissivity · Longitudinal conductance