Appraisal of the Aquifer Hydraulic Characteristics from Electrical Sounding Data in Imo River Basin, South Eastern Nigeria: the Case of Imo shale and Ameki Formations

Abstract

Twenty three vertical electrical sounding data sets were obtained from various parts of the study area in the middle Imo River Basin, using a maximum current electrode separation of 1000 meters. The litho-stratigraphic units within the study area are Imo Formation & Ameki Formation. The sounding data were analyzed with the RESIST software to delineate the sub-surface layering. Three soundings were made at existing boreholes for comparison. The concept of Da-Zarrouk parameters (transverse unit resistance and longit udinal conductance in porous media) was used to determine aquifer hydraulic characteristics. The following values of hydraulic conductivity and transmissivity were obtained for the various formations: For aquifers located within Imo Formation the mean of the hydraulic conductivity K_mean= 2.65 m/day, while the mean of the transmissivity T_mean=46.63m²/day; K_max= 3.13m/day, K_min=2.09m/day; T_max=87.68 m²/day,  T_min=15.54 m²/day. For aquifers located within Ameki Formation, K_mean=2.70m/day; T_mean=80.59 m²/day; K_max=4.65m/day; T_max= 167.14 m²/day; K_min=1.25m/day and T_min=6.08 m²/day. The aquifer thicknesses are (15m—49m) for Imo Formation, (2m—55m) for Ameki Formation.

Keywords: Imo River Basin, aquifer hydraulic characteristics, Dar-Zarrouk parameters.