Hydrochemical Characteristics and Drinking Water Quality Assessment of Phreatic Groundwater in the Northwest of the Sichuan Basin, SW China

In this study, a total of 26 groundwater samples were collected from the northwest of the Sichuan Basin. Statistical analysis revealed that Ca2+ was the predominant cation, followed by Na+, Mg2+, and K+. The anion concentrations followed the order HCO3− > SO42− > NO3− > F− > Cl−. Consequently, Ca-HCO3 was identified as the dominant hydrochemical type in the study area. Geochemical modeling results indicated that silicate weathering and cation exchange processes were the primary factors influencing groundwater hydrochemistry. To provide an accurate assessment of water quality, a Comprehensive Water Quality Index (CWQI) was applied in this study. This novel method combined factor analysis and the entropy-weighted approach to derive integrated weights for water quality calculation. The CWQI results showed that 73.08% of the samples were classified as excellent for drinking, while 26.92% were classified as good. Sensitivity analysis further demonstrated the robustness of the drinking water quality model. The findings of this study could contribute to the enhancement of water quality evaluation in the Sichuan Basin.