HYDRO-GEOPHYSICAL INVESTIGATION OF GROUNDWATER RESOURCES WITHIN ABAKALIKI, LOWER BENUE TROUGH, NIGERIA.
Hydro-geophysical investigation of groundwater resources within Abakaliki, lower Benue Trough was evaluated with the view of determining the groundwater potentials and the aquifer variation in the area. Eight (8) vertical electrical soundings (VES) were carried out using ABEM 4000 SAS Terrameter. Two (2) VES were conducted around area that has existing borehole to enable us check the efficacy of the method. VES data was analyzed and processed using the computer iteration techniques using 1D interpex software. The modeled interpretation from the analysis shows five to six geo-electric layers. The shape of the geoelectric curves in a particular location of the surveyed area depicts characteristics of the subsurface geologic layers. The fractured shale serves as the geologic material that can contain and discharge water. Result reveals that the depth to water table in the study area varies between 11m and 21m and the aquifer thickness is highest in the eastern part of the surveyed area with a thickness value of 7.6meter. The depth to watertable is deepest around staff quarter axis of Onu Ebonyi. Results also reveal a little variation in hydraulic conductivity which ranged between 0.03m/day and 0.19m/day. The wide range of variation in the transmissivity values of the study area could be attributed to the difference to the depth to the fractured shale in the study area and aquifer systems. This area has transmissivity values ranging from 0.0311m2/day to 1.056 m2/day. The result correlates well with the borehole history from the study area.
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