Tracing Spatiotemporal Variability of Water Quality and Surface Water–Groundwater Interaction in Seasonal River Basins Using Source Apportionment Models of Hydrochemistry and Isotopes

Tracing spatiotemporal variability in water quality and surface water–groundwater (SW–GW) interaction is crucial for protecting water resources in arid regions. Focusing on the Ten Kongdui watershed in Inner Mongolia, this study integrated hydrochemical analysis, environmental isotope tracing, and multiple modeling techniques. Specifically, Positive Matrix Factorization (PMF), Self‐Organizing Maps (SOMs), and End‐Member Mixing Analysis (EMMA) were applied to reveal water quality evolution and SW–GW interaction mechanisms. Findings showed that Ca‐Na‐HCO 3 and Ca‐HCO 3 were the dominant hydrochemical facies. Nitrate and fluoride were identified as key limiting indicators, governed by anthropogenic emissions and natural mineral dissolution, respectively. The watershed exhibited significant SW–GW interaction, with groundwater acting as a core component to stabilize seasonal runoff and buffer hydrological fluctuations. Moreover, high surface water contributions to runoff across different hydrological cycles and human influences further confirmed robust regional hydraulic connectivity. These findings provide a scientific basis for precise water resource management and ecological protection in areas sensitive to climate change and anthropogenic stressors.