DETERMINATION OF AQUIFER CHARACTERITICS IN ITEM AREA OF SOUTHEASTERN NIGERIA

ABSTRACT

Hydro-Geo-electrical study of subsurface geology of Item area, South-eastern Nigeria has been carried out involving twenty-four Vertical Electrical Sounding (VES) of which the schlumberger electrode configuration was employed for the field data acquisition. A maximum of half the current electrode separation (AB/2) of 1000m was used. The VES data were interpreted using conventional partial curve matching method to obtain initial model parameters while the computer iterative modelling was obtained using the zohdy software. The study was aimed at the feasibility of potable water borehole, the geology of the southern part of ltem 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. The Eze-Aku and Nkporo Formations appeared at the Northern part of the study area while Ajali and Mamu Formations appeared at the Southern part of the Study area. From the VES data, the variation of aquifer thickness varies from 0.61m at Amaeke to 30.2m at umuakpa. 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 8.3533x10-2. The aquifer conductivity has the highest value of 2.57x10-2m at Ama Okayi and lowest at Okoko with the value of 1.176x10-4m. 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.

Keywords: Hydro-geo-electrical, hydraulic parameters, aquifer and Item Area