RESUMO
The Zuli River is one of the branches of the upper Yellow River, as an inland catchment with semiarid climate in northwestern China, and the formation, evolution, and development of brackish water at such a large scale have remained unclear. This study aims to find clues about the origin and formation mechanism of salty water through multiple methods of hydrochemistry and isotope hydrology. The results show that groundwater is dominantly recharged by precipitation, and the river water was mainly recharged by groundwater discharge. The relatively high tritium content of groundwater (>5.0 TU) clearly suggests the occurrence of a modern recharge and rapid circulation. The dissolution of evaporate minerals, followed by incongruent dissolution of carbonate minerals (dolomite), constituted the main processes controlling groundwater salinization. In addition, the intense evaporation and unreasonable use of fertilizers further increase the TDS of the river, which should be the primary external mechanism of water salinization. PRACTITIONER POINTS: The authors aimed to find clues about the formation mechanism of salty water in an inland catchment of the Yellow River. The results of this research shows that the dissolution of dissolved minerals constituted the main processes controlling groundwater salinization. In addition, the intense evaporation and unreasonable use of fertilizers, which should be the primary external mechanism of water salinization. This work would provide a theoretical basis for government to develop rational utilization of brackish water resources in the study area, which is also significant for understanding the mechanism of water salinization in an inland mountain watershed and even in similar inland watersheds around the world.
