Coupling stable isotopes and glacier mass balance reduces uncertainty in glacio-hydrological modelling

The Urumqi Glacier No.1 (UGN1) and Dongkemadi Glacier (DG) catchments in China, both highly glacierized alpine catchments, provide critical water resources for downstream rivers and are sensitive to climate change impacts. Accurate simulation of glacier runoff processes remains challenging due to limited observational data. Here, we introduce FLEX G -iso, an isotope-aided glacier hydrological model that couples stable water isotopes with glacier mass balance (GMB) to simulate runoff generation and partition runoff components in these catchments. We also assess the transferability of model structures and parameters between UGN1 and DG catchments. Results demonstrate that incorporating stable water isotopes and GMB data enhances the identification of parameters controlling snow and ice accumulation and melt. FLEX G -iso provides more robust partitioning of runoff components, distinguishing throughflow and groundwater, even with limited tracer availability, and improves runoff simulation accuracy (KGE > 0.8) when transferring optimal parameter sets. These findings highlight the potential of isotope-aided modeling to improve both calibration and transferability of glacier hydrological models, offering a robust framework for understanding runoff dynamics in high mountain regions under climate change. • An isotope-aided glacier hydrological model (FLEX G -iso) was developed and validated. • The FLEX G -iso model quantifies runoff components with limited tracer data. • Coupling stable isotopes and GMB enhances model robustness and transferability.