Hydrogeochemical Signatures, Genetic Processes, and Resource Implications of Groundwater in an Arid High-Altitude...

Groundwater serves as an indispensable freshwater source in arid high-altitude urban basins. This study investigates the western Xining city on northern Tibetan Plateau, to elucidate the hydrochemical characteristics, genetic mechanisms, and resource implications of its groundwater in arid urban basins. A comprehensive approach integrating hydrochemical and statistical analyses, the entropy-weighted water quality index, and irrigation suitability evaluation was employed. The results show groundwater in the present arid high-altitude urban basin is generally neutral to weakly alkaline, exhibiting marked spatial variability in total dissolved solids (TDS), with 47.83% exceeding drinking water standards. Along the groundwater flow path, the hydrochemical facies evolve from HCO₃-Ca type to mixed Cl-Mg·Ca type and ultimately to Cl-Ca type, reflecting a clear salinization trend. Groundwater chemistry is mainly governed by silicate weathering, with secondary contributions from carbonate and evaporite dissolution, accompanied by limited cation exchange. Anthropogenic influences, particularly agricultural fertilization, have caused extensive nitrate enrichment, affecting 96% of the samples. River water exhibits excellent quality and is suitable for direct consumption, whereas only 56.5% of the groundwater meets drinking water standards, with the remainder classified as medium to poor quality. Regarding irrigation suitability, river water is highly favorable, and most groundwater is also acceptable. However, certain localities show elevated salinity and sodium hazards, highlighting the need for enhanced management to ensure sustainable water resource utilization. This study elucidates the hydrochemical genesis of groundwater in fragile plateau urban environments and contribute to sustainable local water resource management.