Sustainable Groundwater Management through Integrated Analysis of Remote Sensing, Hydrogeochemistry, and Health Risk in the Farafra Oasis, Western Desert of Egypt

Abstract The Farafra Oasis in Egypt’s Western Desert depends primarily on the Nubian Sandstone Aquifer System (NSAS) for domestic and agricultural water supply. This study presents a hydrogeochemical evaluation combined with a preliminary health risk assessment based on twelve groundwater samples collected in May 2025. Physicochemical parameters, including pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), and major ions (Ca 2 ⁺, Mg 2 ⁺, Na⁺, K⁺, HCO₃⁻, Cl⁻, and SO₄ 2 ⁻), were analyzed to assess groundwater quality and controlling processes. The results indicate that groundwater is dominated by the SO₄·Cl–Ca·Mg hydrochemical facies. Average TDS (299 mg/L) and EC (459 μS/cm) values are generally within World Health Organization (WHO) guideline limits, and groundwater ranges from fresh to slightly hard, with an average pH of 6.6, indicating suitability for drinking and irrigation. Hydrogeochemical interpretation using Piper diagrams, ionic ratios, and Na⁺–Cl⁻ relationships suggests that mineral dissolution and ion-exchange processes are the main controls on groundwater chemistry, with limited evaporative influence. An exploratory classification and regression tree (CART) model identifies EC (485 μS/cm) as a threshold distinguishing relatively fresh from more mineralized groundwater, with bicarbonate and sodium as key variables. Spatial analysis reveals lower salinity in the western oasis and higher salinity in northeastern areas, likely linked to localized agricultural activity. Health risk assessment shows that estimated average daily doses of major ions are generally within acceptable limits, although localized exceedances occur. The Water Quality Index (WQI) classifies most samples as good to excellent. Given the limited sample size and single sampling campaign, the results are indicative, highlighting the need for long-term monitoring and integrated groundwater management.