Geo-electrical Survey for Groundwater Potential of Biu and Environs, North Eastern Nigeria

Abstract

Thirty-six Vertical Electrical Sounding (VES) were carried out to evaluate groundwater potential and aquifer protective capacity of the overburden units using Schlumberger configuration with maximum current electrode of 150m using Petrozenith PZ 02b Terrameter. Data was analyzed using Interpex IX1-D, H-curve type dominates the study area with 41%, k-type and Q-type have 17%, KH-type has 14% and A-type has 11%. Iso-resistivity contour map revealed that major anomaly was found at the eastern part of the study area at Biu with length of 6.2km and width of 2.5km. Geo-electro stratigraphic section revealed that the geologic sequence beneath the study area is composed of top soil, partly weathered/fractured basement, highly Weathered/Fracture basement and presumably fresh basement. Topsoil has resistivity of 50Ωm to 1015Ωm with thickness ranging from 1m to 7m. The weathered/fractured horizons constitute the water-bearing zones referred to as aquifer with a thickness value of 10m to 38m and resistivity value of 23Ωm to 237Ωm. Presumably fresh basement has resistivity values of 4617Ωm to 18313Ωm with infinite depth. Total longitudinal conductance for each potential aquifer zone was used to determine it overburden protective capacity. Four zone have good, twelve zones have moderate and one has poor protective capacity. Twenty VES point were used to produce contour maps for transmissivity and hydraulic conductivity. Hydraulic conductivity and transmissivity varied from 3 to 34m/day and 33 to 919m2/day respectively. Correlation coefficient between transmissivity and hydraulic conductivity give positive correlation which signifies a perfect correlation. VES has proved useful in evaluating the groundwater potentials within and around Biu.