[Major Ionic Features and Their Possible Controls in the Surface Water and Groundwater of the Jinghe River]

To study the hydrochemical characteristics of tributaries of the Jinghe River (Heihe River Basin) and their controlling factors, from 2014 to 2015, 242 samples of surface water and groundwater were collected during the dry and flood seasons from the Jinghe River. After determining the main water chemical ion content by comprehensively using correlation analysis, Piper three-line graphs, and Gibbs graph, the spatiotemporal changes in the hydrochemical characteristics of the Heihe River Basin were analyzed. The results showed that all the water samples in the study area were weakly alkaline. In the dry season of 2014, the cations in the surface water and groundwater were mostly Na⁺, accounting for 56% and 58% of the total cations, respectively. The anions were mainly SO₄^2-, accounting for 33% and 39% of the total anions, respectively. In the other three periods, the main cation and anion components were HCO₃^- and Na⁺, accounting for 44%-46% and 42%-56% of the corresponding totals, respectively. In the dry season, the TDS of surface water and groundwater gradually increases along the river from upstream to downstream. From the dry season to the flood season, the hydrochemical types of the surface water changed from Na-Mg-Cl-SO₄ to Ca-Mg-HCO₃ and of the groundwater from Mg-Cl-SO₄ to Ca-Na-HCO₃. Most of the water chemistry samples were distributed in the middle and upper parts of the Gibbs diagram, indicating that the formation of hydrated chemical ions in the basin was mainly affected by rock weathering and evaporation-enrichment. However, the effects of human activities on water chemistry were more significant in the dry season than in the flood season.