Mountainous waterways account for more than 70% of China's inland navigation mileage.With the development of the modern water transport system,a large number of mountainous waterways urgently require improvement and upgrading.In response to the navigation-obstructing characteristics of mountainous waterways—namely hazardous conditions,rapid currents,sharp bends,shallow depths,and variable flow regimes—a systematic evaluation index system for waterway regulation effectiveness is proposed,which comprises seven key indicators:channel depth,channel width,bend radius,flow velocity,crossflow,backflow,and rapid abatement index.Taking the Hongqi Bridge reach in the middle and lower reaches of the Nujiang River as an example,spatial distributions of the indicators are obtained through numerical modeling.To address the combined navigation obstacles of rapid flow,hazardous conditions,and shallow depths,a regulation scheme involving removal of protruding reefs and dredging of shallow constricted sections is proposed.After the implementation of the regulation scheme,the designed navigation channel meets the required water depth of 1.5 m.Within the regulated reach,flow velocity is greatly reduced,backflow is eliminated,crossflow is controlled below 0.6 m/s,and adverse flow patterns are remarkably improved.The rapid abatement index under all discharge conditions drops below the critical value of 1.0,enabling free navigation of vessels upstream over rapids.The overall regulation targets are fully achieved.Engineering practice verifies that the proposed evaluation index system is scientific and reliable.The spatial distribution of each indicator can intuitively reflect the formation mechanisms of navigation-obstructing rapids and quantitatively assess regulation effectiveness,which provides successful reference cases and evaluation bases for similar mountain waterway regulation projects.