三峡水库不同调控方式对坝下游河道演变影响

受长江上游干支流来水来沙减少、梯级水库蓄水拦沙等多方面因素影响,三峡水库坝下游水沙过程及河道演变发生了明显变化。采用数学模型作为研究手段,开展了三峡水库不同调控方式对坝下游河道演变影响的初步研究。结果表明:不同控泄流量对坝下游河道冲淤总量有一定影响,但影响程度有限,随着水库运用年限的增加,不同控泄方案间的差异有所减小;不同典型河段均表现为河槽冲刷下切、洲滩冲刷萎缩的演变趋势,且随着时间的延长,冲刷强度有所减小,河段的河势总体变化不大,平面形态及深泓摆动幅度较小;控泄洪峰流量减小后,河道演变的趋势变化不大,但大部分河段的河槽冲刷增大,表现为河槽冲深增加和槽宽增大。

Effect of different regulation modes on river channel evolution in downstream of Three Gorges dam

With the impact of the runoff and sediment transportation reduction from trunk stream and tributaries in upper rea-ches as well as the water storage and sediment blocked by upstream cascade reservoirs, the series of runoff and sediment transpor-tation and the evolution of river channel in the lower reaches of TGP dam have changed significantly. The effect of different regu-lation modes of the Three Gorges reservoir on the downstream river channel evolution is studied by using the numerical model cal-culation. The results show that different discharge would affect the erosion and sediment deposit at a limited extent;with the ac-cumulation of reservoir operation period, the difference among different discharge schemes would reduce;scouring is expected in all different sections of river channel and shrink is predicted for islands and beaches;however, the scouring would decrease, river regime tends to be stable and the thalweg swing scope become smaller with time;when the flood peak discharge is cut by the res-ervoir operation, the evolution trend of river channel tends to stable, while scouring increase in most parts of the channel appea-ring as the expansion and deepening of the channel.