Aquifer characterization using vertical electrical soundings and remote sensing: A case study of the Chott Ech Chergui Basin, Northwest Algeria

Abstract

The aim of this study is to provide detailed geological and structural information about groundwater aquifers in the Chott Ech Chergui region using geophysical and remote sensing data. The Chott Chergui region is a large endorheic depression situated in the northwestern part of Algeria. It is submerged in water, and for that reason, it is considered to be a humid zone even though the region is considered to be a semiarid area. The largest quantities of water come from the northern mountains of Saïda and Tlemcen. Some water recharge comes from the Ksour and Amour mountains to the south. Large amounts of this water reach the underground aquifers through a dense fracture network. These water resources are stored in a lithological complex that is composed of three closely related aquifer formations, namely, the continental Tertiary aquifer, the Senonian aquifer and the Aaléno-Bathonian aquifer.The Kheiter and Ain Skhouna areas are known for their gushing water springs that exhibit high flow rates (80 l/s for Ain Skhouna). It is for this reason that we focus on these two regions to understand their flow mechanisms and attempt to construct a conceptual model that illustrates the functional mechanism of the Ain Skhouna spring.This work was accomplished employing a combined approach involving Remote Sensing method and electrical resistivity, specifically, the vertical electrical sounding (VES) technique. The VES technique was used to understand the aquifer geometries and their spatial extents, while the remote sensing results were used to detect some structures and lineaments that favor groundwater exploration. The aquifer geometry was analysed by integrating the results obtained from the interpretations of VES with stratigraphic columns of wells and boreholes using a geographic information system. The results of this study show that three geological levels present aquifer potentialities. The geologic zones are the Aaleno-Bathonian aquifer, which is the most important aquifer in the study area with an average thickness of 250 m, the Senonian aquifer and Tertiary aquifer. The aquifers recharge mainly from fractures in the Saïda and Tlemcen Mountains for the Aaleno-Bathonian aquifer, and from direct infiltration from the accumulated surface waters for the Senonian and Tertiary aquifers. Many water sources are sporadically distributed in the Chott Ech Chergui, but the gushing waters seems to be controlled by E-W accidents, especially in Ain Skhouna hot spring. A schematic model of the spring is presented.