The geological conditions of the Bortala River basin are complex, and the transformation of surface water and groundwater is frequent. It is great significance to study the hydrochemical characteristics and transformation relationship of surface water and groundwater for the reasonable development and allocation of water resources in the basin. Based on 15 surface water samples and 39 groundwater samples collected in April and May 2021, the APCS/MLR model and the combination of stable hydrogen and oxygen isotopes with hydrochemistry were used in this study to analyze the hydrochemical types and the distribution characteristics of hydrogen and oxygen isotopes, the source contribution of chemical components, and the transformation relationship between surface water and groundwater. The results showed that the surface water was mainly HCO3·SO4-Ca type and HCO3-Ca type, and the groundwater was mainly HCO3·SO4-Ca·Na type, HCO3-Ca type, and HCO3·SO4-Ca type. The contribution rates of the dissolution-migration-enrichment factor, human activities factor, environment factor, and native geological factor to the chemical components were 28.8%, 17.7%, 12.0%, and 6.5%, respectively. Bortala River water D and 18O was enriched along the distance, and groundwater D and 18O in the north bank was generally more enriched than groundwater in the south bank as a whole. Under the control of geological conditions such as geological structure and hydrogeological conditions, the transformation of river water and groundwater was concentrated in the middle reaches of the Bortala River, which was generally manifested in both unconfined groundwater and spring overflow in the sides of the recharge river water, and the recharge proportion ranged from 1.0% to 70.9%.
Keywords: Bortala River basin; groundwater; hydrochemical characteristics; surface water; transformation relationship.