干旱区生态环境知识资源中心

Water resources in the Algerian South are rare and difficult to reach because they are often too deep. This is the case of Guerrara which is characterized by an annual precipitation average of less than 60 mm. The water supply is warranted from groundwater, frequently too deep and badly known. The main purpose of the present study is to determine the geometry of aquifer from geophysical data. Fourteen vertical electrical soundings covering the total surface area were carried out by using an arrangement of electrodes called "Schlumberger array." The length of the selected transmission line (AB) was 1,000 m, which allowed a vertical investigation reaching up to 160 m of depth. The analysis of the results shows that the prospected zone is characterized by the succession of layers with different electrical resistivities. A sandstone aquifer characterized by resistivities near 100 Omega m overcoming a limestone aquifer stronger with values that exceed 1,000 Omega m, separated by a conductive layer of clay with average resistivity of 15 Omega m. Distribution map of sandstones thickness shows the structural variations of this horizon allowing an estimation of its hydraulic potential.