Hydrochemical and Stable Isotope characteristics of surface water and groundwater in Xiliugou and Wulagai River basin, North China

Abstract

The investigation of the correlation between groundwater and surface water in terms of water origin and transformation is crucial for comprehending hydrological processes . Focuses on the Wulagai river and Xiliugou river basin located in East and West Inner Mongolia. It employs hydrochemical analysis and stable HO isotopes techniques to investigate the hydrochemical properties of the basin and quantitatively assess the interconversion between groundwater and surface water. The results suggest that the Xiliugou and Wulagai river basins were originally nourished by atmospheric precipitation, with lower δD and δ¹⁸O values in groundwater compared to surface water, attributed to factors such as evaporation, water vapor source, altitude, and latitude. The surface waters in the Xiliugou and Wulagai River exhibit dominance of Na•Ca-SO₄•HCO₃ and Ca•Na-HCO₃ types, respectively, while the groundwater is characterized by dominance of Na•Ca-HCO₃ and Ca•Mg-HCO₃ types, respectively. The water chemistry of surface water and groundwater in the two basins is influenced by water-rock interactions and processes of evaporation and concentration, primarily observed in the dissolution of carbonate rocks and evaporites. Hydrograph separation using End-Members Mixing Analysis (EMMA) revealed that during the growing season, groundwater in Xiliugou was primarily recharged by precipitation (76.87 %) and surface water (23.13 %), while in Wulagai, groundwater was mainly recharged by precipitation (65 %) and surface water (35 %). The presence of comparable hydrochemical constituents and shared regulatory mechanisms between groundwater and surface water within a given basin provides further evidence of a discernible hydraulic interconnection, primarily driven by the replenishment of groundwater through surface water recharge.