Using stable isotopes and major ions to identify hydrogeochemical characteristics of karst groundwater in Xide country, Sichuan Province

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.