Application of Water Quality Index for Drinking and Irrigation Suitability in Arid Zones: A Case Study of the Shallow Aquifer in Oued Souf, Southeastern Algeria

ABSTRACT

In southeastern Algeria, the Oued Souf's shallow aquifer is increasingly affected by environmental dynamics and human‐driven impacts, altering its hydrochemistry, elevating contamination levels, and diminishing water availability amid worldwide climate change. This study examines the sources and drivers of hydrochemical variability and of groundwater quality deterioration, accounting for land‐use changes and human impacts. The quality of groundwater was evaluated using the WQI method to determine its overall condition and its suitability for human consumption. Principal component analysis (PCA) and Pearson correlation were used to interpret the relationships between irrigation indices and hydrochemical variables. At the same time, a Durov diagram was employed to characterize the geochemical evolution of groundwater. The results revealed extremely high salinity (EC = 18,680 μS/cm) and high alkalinity, with Na–Cl facies dominating 80% of the samples, mainly due to reverse ion‐exchange processes and possibly cement‐related contamination. WQI, TDS, and TH values confirmed that the groundwater is unsuitable for drinking. Regarding irrigation, suitability ranged from suitable to conditionally suitable based on SAR, RSC, MH, and PI, whereas KR indicated that most samples are unsuitable. However, when salinity (EC) was considered through the Wilcox and USSL diagrams, together with the PS index, the overall suitability for agricultural use was found to be severely restricted. These results indicate that elevated salinity, rather than sodium hazard alone, represents the principal limiting factor for the use of groundwater in irrigation within the study area. Overall, the findings highlight the progressive deterioration of groundwater hydrochemistry in arid regions, underscoring the need for mitigation strategies, such as cultivating salt‐tolerant crops and pretreating groundwater before use. The findings reveal a decline in the quality of the aquifer, indicating that its appropriateness for both potable and irrigation purposes is substantially restricted under current conditions.