[Hydrochemical Characteristics and Controlling Factors of Surface Water and Groundwater in Wuding River Basin]

Taking Wuding River as the research object, the study explored the hydrochemical characteristics and discussed the source of solute and control factors of groundwater and surface water in the basin, in order to provide a reference for water quality management. Considering the seasonal differences, water samples were collected during the dry season and the flood season. By comprehensively using graphic methods, correlation analysis, and forward deduction models, we analyzed the temporal and spatial evolution characteristics of water chemistry, explored the formation mechanism of water chemistry, and quantified the contribution rates of different sources to solutes. The results showed that the overall water quality was weakly alkaline in Wuding River basin. HCO₃^- and Na⁺ were the main anions and cations in the water, respectively, and the main water chemistry type was HCO₃·SO₄-Na·Ca. The water quality gradually deteriorated along the river course from west to east, and the sampling points that exceeded the level Ⅲ water were mainly distributed in tributaries during the dry season and downstream during the flood season. The cation exchange effect increased the Na⁺ and K⁺ in the water, and NO₃^- and HCO₃^- differed significantly in different seasons, which may be affected by seasonal precipitation leaching soil and land use types. Evaporite weathering and silicate weathering were the main sources of solute contribution in the Wuding River basin, which were 35.0% and 46.5% in the dry season and 46.7% and 42.3% in the flood season,respectively.