Evaluation of Groundwater Potential and Aquifer Protective Capacity Using Dar- Zarrouk Parameters; A Case-Study f Kwara State Polytechnic, Kwara State, Nigeria.

Abstract

This research paper aims to determine the hydraulic properties of the water-bearing layer using parameters derived from the Dar-Zarrouk equation and characterize them into groundwater potential zones. The resistivity values of the weathered and slightly weathered layers which bearing water-bearing layers were added; an average was taken and used as the resistivity of the water-bearing formation in the computation of Dar-Zarrouk parameters in this study area. The curve types identified and the number of occurrences in parenthesis range from H(6), AH(4) and HAH(2). Five lithological layers were identified which are the Topsoil, laterite, weathered rock, fractured basement, and fresh basement. The data reveal generally three to four geo-electric layers, top layer with resistivity value of AB/2 = 1.2m to 3m ranging between 170 and 1322ohm-m. The middle layer has a resistivity value of AB/2 = 2.2m to 20m ranging between 66 and 1890ohm-m and the third geo-electric layer has resistivity values ranging between 100 and 1800ohm-m. The values of resistivity of water bearing formation ranged from 66 to 267 Ωm with an average resistivity value of 152Ωm and the thickness of the water bearing formation ranges from 5 to 61.6m with an average thickness of 17 m. The longitudinal conductance ranges from 0.030 to 0.616Ω-1 , the transverse resistance ranges from 830 to 6160 Ωm 2 . The hydraulic conductivity and transmissivity values range from 1.62 to 33.2 m/day and 66.1 to 267m2 /day respectively with aquifer porosity values ranging from 1.2% - 23.6%. This study shows the importance of combination of different parameters for delineation of groundwater zones in a study area and also the advantage of surface geophysics in estimating hydraulic characteristics of an aquifer where pumping test data are not available and to determine its vulnerability to surface contaminants, also to correlate field/practical analysis in conjunction with theoretical mathematical calculations to delineate groundwater zones. This paper also suggests an imperativeness of not just focusing on the groundwater quantity (potential) but also its quality as it helps to avoid some water prone diseases in this study area