Hydrochemical and isotopic signatures revealing surface-groundwater dynamics: An empirical evidence from the Cherchen River Basin

Water scarcity directly constrains the development of arid inland river basins. Quantifying surface water-groundwater (SW-GW) transformation is critical for refined water resource management. To this end, we selected the Cherchen River Basin as a representative study area. By integrating hydrochemical analysis, isotope tracing, and end-member mixing analysis, we systematically quantified SW-GW interactions under varying spatiotemporal conditions. The results show that: (1) Hydrochemical facies exhibit distinct spatial zonation, transitioning from HCO 3 dominated types upstream to Cl-Na types downstream; (2) Hydrogeochemical processes are controlled by the weathering and dissolution of silicate and evaporite minerals; (3) SW mainly recharges GW in the upstream and downstream reaches, while GW discharges into SW in the midstream, with notable seasonal reversals at certain sections. These findings advance the understanding of hydrogeochemical evolution and SW-GW dynamics in arid inland basins and provide a scientific basis for sustainable water management in similar regions.