基于下游河道中水河槽维持的小浪底水库运用方式研究

Study on the Operation of Xiaolangdi Reservoir Based on Maintaining the River Channel of Median Water of the Lower Yellow River

小浪底水库运用以来,为实现下游河道减淤,水库运用方式以蓄水拦沙和调水调沙运用为主,下游河道输沙能力较低。当前,黄河下游河道适宜的中水河槽规模(泄流能力为4000 m^(3)/s)已形成,长期维持该河槽规模,充分发挥黄河下游河道输沙能力输沙入海,成为当前及今后一个时期水库减淤调度的新要求。根据黄河下游1960—2016年306场非漫滩洪水实测资料,分析不同含沙量级、流量级黄河下游河道的冲淤效率和输沙效率,提出含沙量在60 kg/m^(3)以上的大流量洪水过程在下游河道具有较高的输沙效率,但也容易造成河道淤积。进一步提出基于下游河道中水河槽维持的河道输沙对水库运用的要求,即当下游河道中水河槽泄流能力维持在4000 m^(3)/s左右时,为提高河道输沙能力,小浪底水库可适时增加泄放含沙量不超过100 kg/m^(3)的大流量过程;当下游河道中水河槽泄流能力扩大至4500 m^(3)/s以上时,小浪底水库可适时增加泄放含沙量不超过200 kg/m^(3)的大流量过程;若未来下游河道中水河槽泄流能力缩减至4000 m^(3)/s以下时,小浪底水库调度仍以蓄水拦沙和调水调沙运用为主,以重塑河槽规模。数学模型计算结果表明,小浪底水库运用方式调整可提高下游河道输沙能力,同时减缓小浪底水库和下游河道的淤积,且在更长的时间内维持下游河道泄流能力为4000 m^(3)/s左右的中水河槽。

The Xiaolangdi Reservoir has been mainly used for sediment trapping and water-sediment regulating in order to reduce sedimentation of the lower Yellow River after operation,which results in lower sediment transport efficiency.At present,a suitable river channel scale of median water with the bankfull discharge capacity of 4000 m^(3)/s has been formed in the lower Yellow River.Under this riverbed condition,how to maintain the river channel of median water of the lower Yellow River and give full play to the river sediment transport capacity becomes new requirement to the operation of the reservoir.This paper analyzed the sediment transport efficiency at different sediment concentration levels and discharge levels based on the measured data of 306 non-overbank floods in the lower reaches of the Yellow River from 1960 to 2016 and proposed that the downstream river channel had a higher sediment transport efficiency when the large flow with sediment concentration greater than 60 kg/m^(3),but it was also prone to cause sedimentation in the river channel.The paper further proposed the sediment transport requirement to the operation of the reservoir based on maintaining the river channel of median water of the lower Yellow River.In order to improve the sediment transport capacity of the downstream river,when the bankfull discharge capacity of the downstream river channel was about 4000 m^(3)/s,the Xiaolangdi Reservoir could discharge large-flow processes with sediment concentration less than 100 kg/m^(3).When the bankfull discharge capacity of the downstream river channel was greater than 4500 m^(3)/s,the Xiaolangdi Reservoir could discharge large-flow processes with sediment concentration less than 200 kg/m^(3).When the bankfull discharge capacity of the downstream river channel was less than 4000 m^(3)/s in the future,the Xiaolangdi Reservoir would still mainly trap sediment to reinvent the river channel.The calculation results of the mathematical model show that the adjustment of the operation mode of the reservoir can improve the sediment transport capacity of the downstream river,alleviate the sedimentation of the reservoir and the downstream river and maintain the river channel of median water with the bankfull discharge capacity of 4000 m^(3)/s for a longer period of time.