**Methods:** Eighteen groundwater samples were collected from wells in the El-Fashn District, southwest of Beni Suef, during summer 2018. Field parameters (pH, EC, temperature) were measured in situ. Major cations and trace elements were analyzed by ICP-ES, and major anions by ion chromatography. Multivariate statistical techniques (principal component analysis, PCA; hierarchical cluster analysis, HCA) were applied using SPSS. Hydrogeochemical modeling (Piper diagrams, Gibbs plots, ion exchange indices, saturation indices via PHREEQC, and clay mineral stability diagrams) was performed. Water quality was assessed using the Canadian Council of Minister of Environment Water Quality Index (WQI-CCME) for drinking, and multiple indices (Kelly's ratio, sodium percent, SAR, RSC, magnesium ratio, corrosivity ratio, US Salinity diagram) for irrigation suitability.
**Key Results:** Groundwater pH ranged from 6.88 to 7.42, and TDS from 388 to 5056 mg/L (mean 1768 mg/L), varying from fresh to brackish. Major ions exceeding EPA drinking standards included Na⁺ (max 1067 mg/L, 4.34-fold above limit), SO₄²⁻ (max 1545 mg/L, 5.18-fold), and Cl⁻ (max 1488 mg/L, 4.95-fold). Trace elements Mn (max 1.14 mg/L, 21.8-fold above EPA limit), Fe (max 0.788 mg/L, 1.6-fold), Al (max 0.304 mg/L, 0.52-fold), and Ni (max 0.024 mg/L, 0.2-fold) also exceeded limits in some samples. PCA extracted four factors explaining 83.78% of total variance: Factor 1 (37.78%, salinization: Na⁺, EC, TDS, Cl⁻, PO₄³⁻, K⁺, Ca²⁺, SO₄²⁻), Factor 2 (21.17%, anthropogenic/secondary enrichment: HCO₃⁻, Mn, Ba, Mg²⁺), Factor 3 (16.16%, secondary/micro-nutrient fertilizers: Fe, Co, Mg²⁺, Ba, K⁺), and Factor 4 (8.67%, aluminum fertilizer: Al). HCA identified three major clusters: C1 (Na-Cl facies), C2 (Ca-SO₄ facies with highest TDS, Ca²⁺, Na⁺, SO₄²⁻, Cl⁻, PO₄³⁻), and C3 (Ca-HCO₃ facies with lowest TDS but highest Al, Ba, Co, Cu, Fe, Zn). Piper diagram revealed five water types: Ca-SO₄ (39%), mixed Ca-Mg-Cl (27%), Na-Cl (22%), mixed Na-Ca-HCO₃ (6%), and Ca-HCO₃ (6%). Gibbs plots indicated evaporation and rock-water interaction as dominant processes. Ion exchange was the predominant process (negative chloro-alkaline index), with reverse ion exchange in one sample. Saturation indices showed calcite oversaturation, gypsum near saturation, and halite undersaturation. Clay mineral stability diagrams indicated equilibrium with Ca-smectite and kaolinite. WQI-CCME values ranged from 65.08 (fair, sample G2) to 100 (excellent, samples G10 and G12). For irrigation, most samples were suitable based on Kelly's ratio, Na%, SAR, RSC, and magnesium ratio, but samples G2, G13, G15, G16, and G18 showed elevated sodium and salinity hazards. US Salinity diagram classified samples into C2S1 to C4S4 classes. Corrosivity ratio indicated all samples except G10, G13, G15, and G17 were corrosive.
**Clinical Implications:** This study provides a comprehensive framework for assessing groundwater quality in arid agricultural regions. The findings highlight that while the Quaternary aquifer in Beni Suef is generally suitable for drinking and irrigation in specific areas (northern, central, northwest, and western parts), significant portions are impacted by salinization and anthropogenic contamination from fertilizers and irrigation practices. The identification of specific pollution sources (salinization, fertilizers) through factor analysis enables targeted management interventions. Recommendations include using salt-tolerant crops with good drainage in high-salinity areas, employing corrosion-resistant pipes for water transport, and careful fertilizer management in newly reclaimed lands to prevent further aquifer degradation. The integrated methodology (statistical analysis + hydrogeochemical modeling) is applicable to other arid-region aquifers facing similar stresses.