Delineation of geoelectric parameters for overburden aquifers vulnerability assessment at Birnin Kebbi NW, Nigeria

An approach involving vertical electrical resistivity sounding (VES) data was carried out in Birnin Kebbi and its Environs, with a view to generate geoelectric parameters for lithologic layers identification, determine the Dar-Zarrouk parameters in evaluating the aquifer risk to surface infiltrations and to produce relevant maps that would upgrade our knowledge on the vulnerability assessment of the study area. A total of fourty eight (48) depth resistivity sounding data randomly distributed were acquired using sclumberger array, with half maximum current electrode separation (AB/2) of 100 m, due to shallow, deep and very deep of penetration. The VES were quantitatively interpreted using partial curve matching and computer aided iteration to determine geoelectrical parameters of each station. Results of the study were interpreted with Vertical Electrical Sounding (VES) measurements. The Transverse Resistance (TR) was calculated for each of the VES locations as described using Dar-Zarrouk formula. Thus, the results obtained shows that the thickness of unconsolidated materials overlying the basement (overburden thickness). The study area is characterized by thin and thick overburdens (4.8 m -34.7 m) but mostly thick across the entire area, thus suggesting that the water-bearing horizon across the area is significantly thick. The longitudinal conductance map was used for the overburden protective capacity rating of the study area. The longitudinal conductance (S) value obtained from the area varies from 0.00 0−1 to 0.2 0−1 showing that the area is characterized by low and high values of S across the entire area. The map of the study area shows that about 50% of the area falls within the poor protective capacity, while the remaining 50% constitutes the moderate/weak protective capacity rating. This suggests that the area is characterized by low longitudinal conductance which informed moderate/weak protective capacity rating therefore, the study area is vulnerable to pollution from contaminant sources.