Hydrochemical Characteristics and Transformation Relationship of Surface Water and Groundwater in the Hua County, Guanzhong Plain (China).

Abstract

Understanding the hydrochemical characteristics and interactions between surface water and groundwater is crucial for the development and protection of water resources in the watershed. This research employs mathematical statistics, hydrogen and oxygen isotopes, IsoSource model, and hydrogeochemical simulation to analyze the interactions between surface water and groundwater in the Hua County, Guanzhong Plain, China. The findings revealed that the surface water and groundwater are weakly alkaline and low-mineralization freshwater, and the primary hydrochemical types was HCO₃SO₄·Ca type. The absolute dominance of HCO₃ ^- and Ca²⁺ in both surface and groundwater can be largely attributed to the dissolution of carbonate and silicate rocks. Evaporation led to δD and δ¹⁸O values enrichment in surface water samples from different tributaries, while groundwater samples, though less affected by evaporation, also displayed δD and δ¹⁸O enrichment due to river water infiltration recharge. Overall, the transformation relationship between surface water and groundwater is dominated by surface water infiltration recharge to the groundwater, with recharge contribution rates ranging from 4.7% to 64.5%. Additionally, some surface water samples from the Shidi River were characterized with high fluoride, which may be ascribed to human activities and evaporation. SUMMARY: Surface water and groundwater are weakly alkaline, dominated by HCO₃SO₄·Ca type. Hydrochemical components are primarily controlled by silicate rock dissolution. Surface-groundwater interaction mainly involves surface water infiltration. δ¹⁸O tracing reveals surface water infiltration recharge rates ranging from 4.7% to 64.5%.