Hydrogeological and hydrochemical study of groundwater in the Béni Ounif region (SW Algeria)

Abstract

This research focuses on the Beni Ounif region, located in the southwest of Algeria, covering an area of 42,730 km² with an estimated population of 13,000 inhabitants. The primary goal of this study is to enhance the understanding of the hydrogeology and hydrogeochemistry of the Beni Ounif aquifers through a series of hydrogeological investigations and analyses of groundwater samples collected from the area. The results identify three main aquifers: the Continental Intercalary (CI) aquifer, which is the most significant with a thickness varying between 100 m and 300 m; above it, the Turonian aquifer, which is of lesser interest in the region; and the superficial free aquifer, composed of Quaternary alluvium, varying in thickness from 300 m to 380 m. Water quality assessments using the Water Quality Index (WQI) revealed that the water quality of the superficial aquifer is predominantly good, with portions classified as mediocre (6.67%) and excellent (13.33%). The water from the CI aquifer was primarily deemed suitable for consumption. Agricultural suitability was assessed using the Irrigation Water Quality Index (IWQI), rating most groundwater samples as good or excellent. Industrial evaluations focused on the water's corrosive potential and scaling capacity, highlighting some samples requiring treatment to meet industrial standards. Additionally, hydrochemical signatures and mineralization processes were extensively studied using Piper, Schoeller, and Gibbs diagrams, along with binary diagrams and saturation index calculations. These analyses indicated that mineralization is primarily influenced by the weathering of silicates and carbonates, the dissolution of evaporites, cation exchange, and anthropogenic inputs, primarily affecting water chemistry in these aquifers. This comprehensive understanding aids in the effective management and use of groundwater resources in the Beni Ounif region. The Beni Ounif region faces increasing water demand (8.46 million m³/year), met by a transfer project delivering 30,000 m³/day from the Albien aquifer, while also being highly vulnerable to floods affecting over 241 hectares. An integrated strategy is recommended, including early warning systems, infrastructure reinforcement, urban planning regulations, community awareness, and sustainable water management.