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Karst groundwater is important water resources for local people in southwest China, especially in Xide country, Sichuan Province. Stable isotopes (H and O) that incorporated with major ions of groundwater were used to identify the origin of groundwater, and determine the dominant water–rock interaction processes controlling the hydrogeochemical characteristics of groundwater in the study area. The stable isotopes results indicated that all groundwater derived from meteoric water. The chemical analysis showed that the cold groundwater was HCO3-Ca·Mg type, and the thermal water was HCO3·SO4-Ca·Mg type. The major ions of groundwater combined with the equilibrium stated of the groundwater based on the saturation index (SI), suggested that the hydrogeochemical characteristic of groundwater was mainly governed by dissolution of carbonate minerals and gypsum rocks, and ion exchange. Other factors such as evaporation and anthropogenic activities may also play roles on it. The results revealed the dominant hydrogeochemical processes controlling groundwater water quality in this karst area, which would provide significant insights into the local governments that can make effective policy for groundwater utilization.

In this study, the major chemical compositions of 159 shallow groundwater samples incorporated saturation index (SI) and Principal Component Analysis (PCA) were employed to evaluate the mainly geochemical processes that control the hydrogeochemical evolution of groundwater in a typical karst area, Bijie city, Guizhou Province. The groundwater samples in this study area were dominated of HCO3-Ca, HCO3-Ca-Mg, and HCO3-SO4-Ca types. The PCA suggested that four principal components could explain 88.85% of the total variance of 10 parameters, indicating that the hydrogeochemical evolution of groundwater was mainly controlled by the dissolution/precipitation of carbonates, gypsum, and halite minerals, cation exchange, and anthropogenic activities. To be specific, the enrichment of Ca2+, Mg2+, HCO3− and SO42− in groundwater were primarily affected by the dissolution of dolomite and gypsum minerals, and the role of calcite dissolution was relatively weaker because most groundwater samples were saturated with respect to calcite. Besides, cation exchange was another factor that may affect the concentration of Ca2+ and Mg2+ in groundwater, and the concentration of SO42− can also be influenced by coal mining activity. In addition, the concentrations of Na+ and Cl− in groundwater were likely influenced by the dissolution of halite, cation exchange, and human activities.