Characterization of Crystalline Aquifers in Ouaddaï Division (East of Chad) Using Electrical Resistivity Method: A Case Study of Waguiré and Anourchi

Abstract

This study aimed to locate suitable aquifers that can be exploited with their structural and hydraulic characteristics. So for this aim, combination of geoelectrical and drilling techniques was used. Eight electrical trailing and Vertical Electrical Soundings (VES) were carried out with Syscal R1 - Plus resistivimeter, using Schlumberger array. VES data were interpreted using the Ipi2win software, and geohydraulic parameters (conductivity, transmissivity, and porosity) were estimated based on geoelectric parameters computed. Results show four favorable shapes of electrical trailing (W, U, V, and H -shapes) and four types of VES curves (H, HA, QH and HKH). Three to five geoelectric layers were delineated from analysis of VES curves with aquifer resistivity influenced by clay content, varying from 6.09 to 33.84 Ω.m and thickness from 5.54 to 17.35 m. Computed hydraulic conductivity, transmissivity, and porosity vary from 14.19 to 70.93 m/day, 92.36 to 429.13 m²/day, and 37.44 to 44.68% respectively. The groundwater potential of the area ranges from moderate to high potential. Based on these geohydraulic parameters, two points (VES4 and VES7) were chosen to drill a hole. Drillings were a success and yield ranging from 2.72 m3/h to 3.12 m3/h. This study reveals that geohydraulic parameters could be an alternative to choose where to drill a positive borehole in the area with a similar geological context.