Hydrochemical evolution and spatio-temporal dynamics of irrigation water quality in the Bay of Algiers aquifer (Algeria)

Abstract

This study assesses the spatio-temporal evolution of the quality of groundwater intended for irrigation in the coastal aquifer of the Bay of Algiers (northern Algeria) during three sampling campaigns conducted in 2006, 2020 and 2025. An integrated approach combining physicochemical parameters, the main irrigation water quality indices, hydrochemical diagrams, multivariate statistical analysis and geographic information systems was used to characterise the controlling hydrochemical processes and assess the suitability of the water for irrigation. The results reveal a progressive deterioration in water quality, marked by increases in electrical conductivity, total dissolved solids, sodium and chloride. The irrigation water quality index decreased from 64.82 in 2006 to 55.19 in 2020 and then to 36.08 in 2025, indicating a progressive reduction in irrigation suitability. The Piper and Gibbs diagrams, together with hydrochemical indices and spatial mapping, highlight an intensification of salinisation processes driven by the combined effects of water-rock interaction, evaporation-crystallisation, an increasing influence of seawater intrusion and anthropogenic pressures. These findings underline the need for regular monitoring and sustainable management strategies to preserve groundwater resources and limit salinisation risks in coastal aquifers.