In this study, the hydrochemical characteristics of surface water in the Yarkant River Basin of Xinjiang and their controlling factors were analyzed using a Piper trilinear diagram, Gibbs diagram, saturation index, ion proportional relationship, and other methods. The study has significance to the surface water resources in the basin for development and utilization. The results indicated that the pH of the surface water ranged from 7.40 to 8.33, with a mean value of 7.92, which was weakly alkaline. The mean value of the total dissolved solids (TDS) of the river, canal, and reservoir water exhibited an increasing trend. The TDS mean of the river was 429.24 mg·L-1, higher than the average value of rivers worldwide (115 mg·L-1). The hydrochemical types of the river water were predominantly HCO3·SO4-Ca·Na and SO4·HCO3·Cl-Ca·Na·Mg types, of the canal water was mainly HCO3·SO4·Cl-Ca·Na type, and of the reservoir water was mostly the SO4·Cl-Na·Ca type. The TDS of the river water along the Yarkant River and Tiznap River demonstrated a continuous increase and fluctuation trend, respectively, while the variation of the primary ions was relatively complex. The primary ions of surface water were mostly influenced by rock weathering, evaporation crystallization, and cation exchange, in which gypsum and rock salt were predominantly dissolved in the process of rock weathering. In addition, human activities had significant effects on the chemical composition of the surface water downstream.
Keywords: Yarkant River Basin; chemical origin; hydrochemistry; ion source; surface water.