丹江口水库蓄水以来汉江中下游河床冲淤变化研究

Study on riverbed erosion and deposition change in middle and lower reaches of Hanjiang River since impoundment operation of Danjiangkou Reservoir

丹江口水库蓄水运用后,汉江中下游河床发生了显著调整。为了加深对水库调蓄影响下汉江中下游河床整体冲淤规律的认识,根据大量实测资料,对汉江中下游水沙与河床冲淤变化进行了较为系统的分析。结果表明:丹江口水库蓄水运用后,汉江中下游洪峰削减,枯水期流量增大,中水期延长,径流年内分配更加均匀,坝下游输沙总量大幅度减少。南水北调中线工程运行后,径流年内分配更趋均匀,坝下游输沙量进一步减少。1978~2020年,丹江口至河口河段平滩河槽冲刷了10.75亿m^(3),冲刷强度自上而下逐步减小;中游丹江口至碾盘山河段仍是冲刷发展最为剧烈的河段。近期河床演变分析结果表明:丹江口至襄阳河段洲滩变化较大,江心滩面积有所淤长且整体下移;襄阳至碾盘山河段洲滩、汊道基本稳定,河道游荡性减弱;碾盘山至仙桃河段深泓线横向摆动频繁,洲滩冲淤变化较为剧烈;仙桃至河口河段河床演变强度相对较小,但局部弯道有裁弯取直现象发生。分析成果可为汉江中下游防洪减灾、规划设计、河道治理、采砂管理、航道整治等提供参考。

Since the impoundment operation of the Danjiangkou Reservoir,the riverbed of the middle and lower reaches of the Hanjiang River adjusted significantly.To deeply understand the riverbed evolution law under the impact of reservoir regulation,we analyzed the changes of flow,sediment,riverbed erosion and deposition in the middle and lower reaches of Hanjiang River based on long time series of measured data.After the initial impoundment of Danjiangkou Reservoir,the flood peak in the middle and lower reaches of Hanjiang River reduced,the flow rate in dry season increased,and the middle water period prolonged.So the annual distribution of runoff was more uniform,and the total sediment transport downstream of the dam was greatly reduced.After the operation of the Middle Route of South-to-North Water Diversion Project,the annual runoff distribution becomes more uniform,and the sediment discharge in the downstream of the dam furtherly decreases.From 1978 to 2020,the bankfull channel of Danjiangkou to Hekou reach scoured 1.075 billion m^(3),and the scour intensity gradually decreased from upstream to downstream,and the middle reach of Danjiangkou to Nianpanshan reach was still the most intensely scoured section.The results of recent river bed evolution analysis showed that the sand bars and beaches in Danjiangkou to Xiangyang reach changed greatly,and the beach area in river center became large and moved downstream in overall.The beaches and branches of Xiangyang to Nianpanshan reach were basically stable,and the river channel wandering was weakened.The horizontal swing of the thalweg line from Nianpanshan to Xiantao reach was frequent,and the erosion and deposition of the beach were more intense.The evolution intensity of riverbed from Xiantao to estuary reach was relatively small,but the local bend had the phenomenon of river bend straightening.The analysis results can provide reference for flood control and disaster reduction,planning and design,river regulation,sand mining management and waterway regulation in the middle and lower reaches of Hanjiang River.