黄河下游河道主槽容积近50年变化过程及模拟OA

The main channel storage capacity is directly related to the flood control safety and sediment transport capacity of the Lower Yellow River.Affected by channel sedimentation changes,the specific variation patterns of the main channel storage capacity in the Lower Yellow River over the past 50 years remains unclear.This study is based on annual post-flood cross-sectional data of 91 major sections from Tiexie to Lijin in the lower Yellow River from 1970 to 2020.Using the frustum method,the main channel storage capacity of each river section was calculated,revealing its spatiotemporal evolution patterns.A delayed response simulation method for main channel storage capac-ity was established,and the impact of the Xiaolangdi Reservoir on the main channel storage capacity was evaluated.The results show:(1)The main channel storage capacity and storage capacity per unit length exhibited a trend of"slight increase(1970-1985)-significant decrease(1985-2000)-significant increase(2000-2020)."Spatially,the wandering reach had the largest main channel storage capacity with notable fluctuations.However,the proportional distribution among all sections remained relatively stable,with average proportions of 55％,19％,and 26％for the wandering,transitional,and meandering sections,respectively.After the operation of the Xiaolangdi Reservoir,the main channel storage capacity increased significantly,from 1.039 billion m3 in 2000 to 2.747 billion m3 in 2020,with an average annual growth rate of 5％.(2)The delayed response model,based on annual average flow and sedi-ment concentration,effectively simulated the evolution of main channel storage capacity(R2=0.8480-0.9325,MAPE=3.72％-10.02％).The time to reach quasi-equilibrium for the main channel storage capacity in the lower Yellow River ranged from 7.6 to 13.2 years.(3)With the Xiaolangdi Reservoir in operation,the main channel stor-age capacity increased by 1.588 billion m3 compared with that in 1999,whereas without Xiaolangdi,it would have increased by only 0.509 billion m3,marking a difference of 1.079 billion m3.This indicates that the main channel expansion is the combined effect of soil and water conservation and sediment trapping by the Xiaolangdi Reservoir.Soil and water conservation contributes approximately 30％to the increase in the main channel storage capacity of the lower reaches,while the Xiaolangdi Reservoir accounts for about 70％.The research results help to reveal the mecha-nism behind changes in main channel storage capacity and provide support for maintaining the storage capacity and achieving the long-term stability of the Yellow River.