Hydraulic Conductivity Estimates of Imo River Basin’s Aquiferous layers, Southeastern Nigeria Using Empirical Equations Derived from Electrical Resistivity Data

This study was carried out to determine the equation (model) that fits best to the hydraulic conductivity values measured directly from pumping test data from monitoring wells. Three different electrical resistivity empirical equations were used to estimate aquifer hydraulic conductivity of Imo river basin, southeastern Nigeria, using surficial geo-sounding data. Two hundred (200) vertical electrical sounding (VES) data were obtained with forty-five (40) available pumping test data that were acquired from monitoring wells within the study area. Similarly, forty of the two hundred VES data were acquired close to the monitoring wells for parametric and correlation purposes. Three empirical resistivity model equations (N_ Model, H_ Model, and M_ Model) were used to estimate aquifer hydraulic conductivity across the study area. Estimates of the aquifer hydraulic conductivity from the three models revealed that the hydraulic conductivity ranges between 0.23- 26.43m/day with a mean value of 6.15 m/day for N_ Model. For H_ Model it ranged between 0.07 and 5.22m/day with a mean value of 1.03m/day and for M_ Model it ranged between 1.03 and13.42m/day with a mean value of 4.19m/day . The Aquifer hydraulic conductivity values estimated from the M_model when compared with the values from the pumping test showed a strong coefficient of determination (R2 = 0.82) while N_ Model and H_ Model revealed very poor correlations with the pumping test data, with negative correlations of -0.03 and -0.3 respectively. The results of the t _test revealed that there is no significant difference between the estimated hydraulic conductivity values from M_Model and pumping test data. These findings have therefore revealed that geologically constrained empirical resistivity equations are reliable for the estimation of aquifer hydraulic conductivity from surface resistivity data. The reason for the poor correlation of the N_Model and H_Model with the pumping test data in the study area is because local geology of the study area was not considered by the models.