Estimating aquifer transmissivity from geo-electrical sounding
AbstractA geophysical survey was carried out at Kaduna Polytechnic Senior Staff Quarters using Direct Current Electrical Resistivity method. The objectives were to determine different subsurface geoelectric layers, the aquifer units and the estimation of Transmissivity of the aquifer. Sixty-six Schlumberger Vertical Electrical Soundings (VES) were carried out using a maximum electrode separation of 200m.Data analysis and interpretation of the field curves by computer modeling proposes a distinctive 3-4 geoelectric layer situations. This includes the topmost layer which consists of laterite, river sand and gravel. This formation is followed in succession by clayey sand, weathered transition zone/ fractured layer and the fresh basement. Qualitative interpretation indicates that the weathered/fractured Basement constitutes the main aquifer unit. Aquifer resistivity range from 4.26 ohm-m to 755.3 ohm-m with maximum thickness of 52.25m. A maximum 55.52m depth- tobasement was obtained in the study area. Based on the model obtained, aquifer Transmissivity was calculated and was used to delineate the study area into prospective low and high groundwater potential zones. In order to test the reliability of the results, the calculated Transmissivity values were compared with those obtained from pumping test analysis, and a linear regression coefficient of 0.94 was obtained.
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