CARACTERISTIQUES, EVALUATION ET GESTION DE LA NAPPE ALLUVIALE DE OUED BISKRA

Abstract

The region of Biskra, located in the South-East of Algeria, is characterized by an arid climate, marked by low precipitation and rare flood events. Despite these conditions, the alluvial aquifer of Oued Biskra represents an immense underground water treasure, with an estimated storage volume of 30 million cubic meters. Consequently, its origin and functioning raise questions and ambiguities. Within the framework of this thesis, an in-depth investigation was conducted using various approaches: hydrological, hydrogeological, hydrochemical, geophysical, and structural. The objective was to address the interrogations and ambiguities regarding the origin of groundwater in the Oued Biskra alluvial aquifer. By hour-by-hour monitoring of the variation in the piezometric level, made possible by the installation of digital recorders in two boreholes, reveals the absence of influence from local Biskra precipitation on piezometric level variations. In contrast, it highlighted a delayed response of the aquifer to precipitation recorded in the Aurès massif, specifically at the Bouzina and Menaa stations. Geophysical prospection using vertical electrical sounding, based on measuring the resistivity of geological formations, reveals the presence of highly conductive zones along the central axis of the aquifer and on the right bank. These zones suggest the presence of a water-saturated area with high mineralization and elevated temperature, thus supporting the hypothesis of an ascending water supply (intrusion) from deeper formations. Physicochemical analysis of groundwater in the alluvial aquifer indicates aquifer recharge by mesothermal waters (31°C) originating from the Turonian carbonate aquifer through the contact surface between the Turonian and alluvial aquifer at Djebel Bou Rhezel. The Oued Biskra alluvial aquifer, like many underground water reserves in arid zones, symbolizes resilience and hope. Its preservation is a challenge we must collectively address to ensure a sustainable future for communities dependent on this vital resource.