Determination of Aquifer Characteristics in Item Area of Southeastern Nigeria Using Vertical Electrical Sounding

Abstract

Aquifer characteristic study of subsurface geology of Item area, South-eastern Nigeria has been carried out using twenty-four Vertical Electrical Sounding (VES) of which the schlumberger electrode configuration was employed. A maximum of half the current electrode separation (AB/2) of 1000m was used. The study aimed at the feasibility of potable water borehole, the geology of the southern part of the study area from that of the northern part bedevilled by groundwater problems. The study area has four geological formations which include Ajali Formation, Mamu Formation, Nkporo Formation and Eze Aku Formation. From the VES data, the aquifer thickness varies from 0.61m to 30.2m, the transmissivity of the aquifer ranges from 0.104m²/day at the Northern part to 78.66m²/day at the Southern part of the study area. The parameters used in describing the aquifer characteristics showed that the longitudinal conductance of the aquifer is highest at Ama okayi with the value of 8.3533×10^-2W. The aquifer conductivity has the highest value of 2.57×10^-2Wm at Ama Okayi and lowest at Okoko with the value of 1.176×10^-4Wm. The transmissitivity of the aquifer ranges from 78.657m²/day at Okoko Item to 0.0976m²/day at Ameke. Thus a better idea of groundwater potentials of the area has emerged from the geophysical data of the area. The downward continuation shows a progressive decrease in resistivity with depth. The study has proven that the Northern part of the study area has serious underground water problems. The southern part which include Okoko, Amangwu, umuakpa and Amaokwe A2 may have productive borehole with effective depth of 40m (132 feets) to 152m (501.6 feets) though thorough hydrochemical investigation is recommended to ascertain the water quality of the aquifer system within the area.