汉江兴隆枢纽坝下枯水位下降成因浅析

Cause Analysis of Decline of Low Water Level Downstream the Dam of Xinglong Hydro-junction on Hanjiang River

汉江兴隆水利枢纽运行后,500~800 m^(3)/s流量下,2021年较运行前坝下水位累计下降2.47~2.55 m,对工程安全及效益发挥带来不利影响。深入研究枯水位下降成因,发现南水北调中线调水及补偿工程实施后,汉江中下游水沙条件变异,“清水下泄”导致河床冲刷;枢纽建设致使坝下局部河势调整,深泓摆动频繁、主流线坐弯延长、过水面积及河槽容积增大;局部航道整治工程的实施促使原滩体萎缩、新主槽刷深;引江济汉补水工程增强了中枯期水流冲刷动力等,上述因素综合导致兴隆坝下枯水位显著降低。

During the operation of the Hanjiang Xinglong hydro-junction,the water level below the Xinglong dam has experienced a cumulative decrease of 2.47-2.55 m under the flow rate of 500-800 m^(3)/s,unfavorable for safety and operation.A comprehensive analysis reveals that the declining water level can be attributed to several factors.The Middle Route of the South-to-North Water Transfer Project and its associated compensation measures gave rise the changes of water and sediment conditions in the middle and lower reaches of the Hanjiang River.This resulted in riverbed scouring due to the clear water discharge.Additionally,the construction of the Xinglong hydroproject caused adjustments to the local river regime.Consequently,the downstream thalweg migrated back and forth,leading to bending and lengthening of the mainstream line.Furthermore,the discharge area and channel volume experienced significant increases.The implementation of waterway regulation measures also resulted in the shrinkage of the original shoal and the rapid deepening of the new main channel.Last but not the least,water diversion project from the Yangtze River to the Hanjiang River intensified the scouring force of water flow during medium and dry seasons.These factors collectively contributed to the noticeable decline in low water level in the downstream of the Xinglong dam.