Application of Vertical Electrical Sounding (VES) For Groundwater Exploration in College of Education, Afaha Nsit and its Environs, Southern Nigeria

Abstract

Surface geo-electrical survey using vertical electrical sounding (VES) method has been carried out in College of Education, Afaha Nsit and its environs in North-East Senatorial District of Akwa Ibom State in order to determine the aquifer characteristics and groundwater potential of the area. Fifteen vertical electrical sounding were carried out within the area of study with the SSP-ATS-MRP model of an IGLS (Integrated Geo-instruments and Services) resistivity meter employing schlumberger array configuration. The maximum current electrode separation was 400 and 600 in some cases. Interpretation of the VES data by partial curve matching technique aided by computer modelling using a computer inversion software (RES2DINV SOFTWARE VERSION 3.57.37) was used. The interpretation of the vertical electrical sounding (VES) data revealed three to five geoelectric units with depth to the aquiferous layers ranging from 46.3 m to 122.0 m and resistivity of the saturated layers varying between 616.6 and 1,111.9  ohm-m. Aquifer characteristics such as aquifer conductivity (σ), Transverse resistance (R), longitudinal conductance (S) and hydraulic conductivity (K) for all the VES points were computed. σ varies from 0.0001797 – 0.00145 mhos, R from 12,406.6 – 81,127.8 Ωm, S from 0.009 – 0.078 Ωm and K from 7.76  80.35 m/day. Computation of aquifer transmissivity values based on the results obtained showed a wide variation from 276.584 m2/day to 3,376.219 m2/day. The relationships and implications are discussed.