The Oligocene–Pleistocene aquifer system in West Mallawi, El Minya Governorate, Egypt, serves as a critical groundwater resource supporting domestic, agricultural, and industrial activities in a region characterized by aridity and scarce surface water availability. Rapid population growth and increasing dependence on groundwater for irrigation have intensified concerns about aquifer depletion and deteriorating water quality. This study provides one of the first comparative hydrochemical assessments of groundwater quality between 2016 and 2024 in the under-monitored West Mallawi aquifer, integrating established multivariate statistical and geochemical modeling techniques within a consistent analytical framework to evaluate changes between two sampling campaigns. Key physicochemical parameters—including pH, electrical conductivity (EC), total dissolved solids (TDS), and major ion concentrations—were evaluated using geochemical modeling, multivariate statistics, and water-quality indices (WQI). Results indicate a marked decline in groundwater quality between the two sampling periods; because the dataset comprises two discrete campaigns rather than a continuous time series, these results describe a comparative change between 2016 and 2024 rather than a verified long-term trend. While pH remained relatively stable (7.6–7.8), EC increased from 1217 to 1327 µS/cm and TDS from 779 to 849 mg/L, both exceeding WHO (2022) drinking-water limits and the Egyptian national standards. Chloride concentrations rose sharply (110 → 287 mg/L), whereas sulfate levels decreased markedly (298 → 89 mg/L). The dominant hydrochemical facies, SO₄–Cl–Na, reflects evaporation, evaporite dissolution, and minor carbonate interaction as key controlling processes. Multivariate analysis of physicochemical variables showed an increase in the variance explained by PC1 from 49.9% (2016) to 60.9% (2024), consistent with an increased influence of salinity-related hydrochemical processes. Groundwater quality deteriorated, with WQI classifications shifting from predominantly Good (WQI 0–50) in 2016 to predominantly Very Poor (WQI 75–100) in 2024. Irrigation water quality also deteriorated due to rising salinity (2490- 3980 µS/cm) hazards. Furthermore, the proportion of samples meeting FAO livestock and poultry water-quality standards decreased from 95.3% (41/43 samples) in 2016 to 86.0% (37/43 samples) in 2024, underscoring mounting salinity stress on agricultural practices. Elevated Cl⁻/HCO₃⁻ ratios in 25 samples as of 2024 are indicative of moderate to severe contamination, although, in the absence of independent tracers (e.g., nitrate or isotopic data), this attribution should be regarded as a plausible inference rather than a confirmed source diagnosis. These findings point to increasing vulnerability of the Oligocene–Pleistocene aquifer between the two study periods and underscore the value of sustainable groundwater management and continuous, higher-frequency monitoring to safeguard water resources in West Mallawi.