Multivariate Statistical Analysis and Structural Sovereignty for Geochemical Assessment and Groundwater Prevalence in Bahariya Oasis, Western Desert, Egypt

Abstract

The Bahariya Oasis is an example of an extremely hyperarid environment and it is characterized by an extensive nonrenewable Nubian Sandstone Aquifer System (NSAS), which is deemed the crucial provenance for agrarian and national development ventures. The present work aimed to assess the groundwater occurrences in the NSAS, and to document the main factors that control the geochemistry of the groundwater in the Bahariya Oasis. Groundwater samples were collected from 52 locations in April 2019 and were analyzed for a total of 13 water-quality physicochemical parameters. A diverse geological and structural setup has greatly impacted the groundwater flow pattern and has diverted it towards the NE by the great Bahariya anticline structure, the ENE-oriented Bahariya mid dextral strike-slip fault, and NE-striking normal faults, while NW-oriented normal faults cause the groundwater to diverge perpendicular to the groundwater flow lines. The groundwater is highly contaminated by trace metals (Fe2+ and Mn2+), which exceed the permissible limit for different purposes. Conventional graphical plots and geochemical modeling integrated with multivariate factor analysis (FA) revealed that the chemical composition of the groundwater is strongly affected by its interaction with the lithologies of the NSAS. The dissolution of aquifer host rocks (carbonates and iron oxides) and chloride salts through the infiltration of groundwater, and the incorporation of cations by the ionic exchange of Na+ by Ca2+ in clay minerals, emerged as worthy mechanisms for the groundwater development. Furthermore, the region’s rapidly increasing population, agricultural expansion, and the associated anthropogenic practices have generated a need for groundwater-quality assurance as a prime source of the water supply. Consequently, reducing the effects of the NSAS’s unsustainable extraction requires long-term monitoring and the ongoing evaluation of the groundwater.