Electro-geohydraulic estimation of shallow aquifers of Owerri and environs, Southeastern Nigeria using multiple empirical resistivity equations

Estimates of the geohydraulic parameters of the aquifers of Owerri and environs were carried out using different empirical resistivity equations with the objective of evaluating the predictive capabilities of the various equations. Forty Vertical Electrical Sounding (VES) data were acquired with a maximum half-current electrode spacing of 500 m using the Schlumberger electrode configuration. Aquifer resistivity across the study area varies from 330 to 78,100 Ωm with a mean value of 9465.8 Ωm. Aquifer depth ranges from 22.5 to 91.8 m with a mean value of 61.79 m while aquifer thickness across the study area ranges from 10.8 to 77.0 m with an average value of 36.72 m. The Dar-Zarrouk parameters revealed that the transverse resistance ranges from 12,276 to 2,297,120 Ωm2 with a mean value of 330,297.01 Ωm2 while the longitudinal conductance ranges between 0.000214 and 0.529231 Ω−1 with a mean value of 0.01323Ω−1. Aquifer hydraulic conductivity values vary from about 2.97–58.55 m/day with a mean value of 15.55 m/day while aquifer transmissivity values vary from about 37.433–7004.61 m2/day with a mean value of 1007.18 m2/day. Aquifer storativity values across the study area vary from 0.0000324 to 0.000231 with a mean value of 0.00011 while aquifer hydraulic diffusivity values ranged between 335,425 and 79,383,443.33 with a mean value of 9,621,354.647. Model ranking using statistical analysis revealed that out of the three different equations used for estimating hydraulic conductivity in the study area, the New Model equation is the best alternative in the absence of pumping test data.