The Yibin-Jiangjin reach of the upper Yangtze River navigation channel is impacted by the operation of the Xiangjiaba Dam and unregulated sand mining activities.Although there is a unified understanding of unilateral changes in inflow variation,daily regulation effects,and topographic changes,there is a lack of research on the comprehensive impact of water level,especially the dry season water level that affects the smooth operation of the channel,and a lack of overall understanding of the change trend of low-water level.By analyzing the water level data from Zhutuo hydrological station and comparing the water level and flow rate relationships along the main waterway,this study reveals low-water level variations in the Yibin-Jiangjin reach since the impoundment of Xiangjiaba.Pre-2015 (Yibin section in 2014)：Low-water levels increased synchronously with rising dry-season discharges.2015-2020：Significant reduction in low-water levels occurred under equivalent discharges;while minimum discharges fluctuated moderately,minimum water levels exhibited an overall declining trend.Post-2020：Both dry-season discharges and water levels tend to stabilize.Before and after impoundment in Xiangjiaba,as of 2024,the water level of the excellent river section with a guaranteed rate of 98% over the years has slightly increased,and the Zhutuo Station has increased by 0.21 m.The minimum water level is basically the same as pre-impoundment conditions.In typical shoal sections (Guanyinbei,Zhengjialiang,Huanggan),low-water levels decreased substantially,with cumulative reductions of 0.60-0.84 m (at discharge of 2,900 m3/s).Water levels frequently fell below the navigation reference plane,indicating deteriorating channel conditions.The analysis demonstrates that anthropogenic riverbed morphological changes have largely offset the benefits of increased flow.These findings provide critical references for channel maintenance and management strategies.