Evaluation of Hydrogeomorphic Dynamics' Influence on Fish Ecological Status in the Upper Yellow River: An Ecohydraulic Modelling Approach for Braided River Management

ABSTRACT This study examines the relationship between hydrogeomorphic processes and the ecological status of the endemic fish species, Schizopygopsis pylzovi Kessler, 1876, and Platypharodon extremus , Herzenstein, 1891, in the Upper Yellow River. Stream and sediment supply fluctuation increasingly impacts fish distribution and habitat quality in the source of the Yellow River. Nevertheless, the specific effects of hydrogeomorphic dynamics on the S. pylzovi and P. extremus species remain insufficiently understood. Utilizing an ecohydraulic modelling framework that integrates hydrodynamic, habitat suitability and sediment transport models within the TELEMAC‐2D module, we evaluated the overall hydrogeomorphic and habitat changes from 1987 to 2017 across the Dari, Guide and Maduo Reaches. We found that intensified anthropogenic activities (e.g., river impoundment, channelization and gravel mining) led to increased habitat fragmentation, particularly in the Guide Reach, which experienced the most significant reduction in channel width. Additionally, the study indicated that suitable habitats for S. pylzovi and P. extremus are supported at medium‐ ( Q 2 = 830 m 3 /s) and high‐discharge ( Q 3 = 1680 m 3 /s) conditions, which achieve a habitat suitability index of 0.7 to 1.0 in the Dari and Maduo Reaches. In contrast, owing to the reduced channel's width and the overall fragmented ecological quality of the reaches, the habitat suitability for S. pylzovi in the Guide Reach further declined in 2017 (post‐dam operation period) under low‐discharge conditions ( Q 1 = 192 m 3 /s). This research explains the interactions between fluvial morphology, hydrodynamic conditions and fish dynamics, which are crucial for effective river management strategies.