Hydrochemical characteristics and influencing factors of the surface water and the groundwater in the Mingyong River Basin of the Meili Snow Mountains

Major chemical ionic components in water serve as indicators of natural factors in the areas traversed by water bodies, and are thus widely used to elucidate key hydrogeochemical processes, including rock weathering, aquatic evaporation-crystallization, and the input of precipitation-derived materials into river basins. A total of 208 water samples were collected between August 2021 and August 2022 to investigate the hydrochemical characteristics and their influencing factors of the surface water and the groundwater in the Mingyong River Basin. To systematically analyze the data, we combined hydrogeochemical and statistical methods: descriptive statistics characterized ion concentration and physicochemical parameter distributions; Piper trilinear diagrams classified hydrochemical types; Pearson correlation analysis assessed ion-ion and ion-TDS dependencies; Gibbs diagrams and ion ratio analysis identified solute sources; and the absolute principal component score-multiple linear regression (APCS-MLR) model quantified the contribution rates of different influencing factors. The results revealed that the dominant cations in the surface water and groundwater are Ca²⁺ and Mg²⁺, while the dominant anions are HCO₃^- and SO₄^2-. The groundwater exhibits an extended residence time within rock strata, facilitating prolonged interaction with soluble minerals and intensifying the water-rock reaction process, thereby resulting in higher levels of electrical conductivity (EC), pH, and total dissolved solids (TDS) than those in the surface water. Secondly, the parameters of the surface water and groundwater indicate positive correlation. The weathering of rocks constitutes the primary solute source in the water of the basin. The hydrochemical composition of the basin water is primarily influenced by both carbonate and silicate rocks, with a minor contribution from evaporite rocks. The water bodies in the basin are affected by anthropogenic activities. The surface water is influenced by four sources, namely lixiviation-enrich, human activities, geological environmental, and unknown sources. The groundwater is influenced by five sources, namely lixiviation-enrich, primary geological, human activities, geological environmental, and unknown sources.