长江上游不平衡水沙输运对三峡库区泥沙淤积影响

Influence of Non-Balanced Water and Sediment Transport in the Upper Yangtze River on Sediment Siltation in the Three Gorges Reservoir Area

2003~2017年以三峡水库为核心的长江上游水库群运行和联合调度从宏观上改变上游河流泥沙时空分布规律,金沙江已不是三峡入库泥沙最大供沙区;长江上游水沙输运集中在汛期5~10月,1956~2002年水沙峰值基本同步,而三峡水库蓄水后2003~2017年水沙峰值不同步,流量特性曲线由顺时针转为逆时针,出现滞后现象。入库泥沙锐减后并未降低三峡库区细颗粒泥沙淤积率,2014~2017年汛期5~10月淤积率增加至85.2%,其中d<0.031 mm的极易发生絮凝的泥沙所占比例最高(63.5%,2009~2013年),典型河段现场观测到大量泥沙絮团,所以三峡库区极可能存在细颗粒泥沙絮凝。入库水沙不平衡也使得朱沱-清溪场河段出现泥沙冲刷。

with operation of reservoirs in the upper Yangtze River with the Three Gorges Reservoir as the core on the period of 2003-2017,the temporal and spatial distribution of sediment in upper Yangtze River has been changed Macroscopically,Jinsha River is no longer the largest sediment supply area for the TGR.The water and sediment transport in the upper Yangtze River is concentrated in the flood season from May to October,the peak of water and sediment between 1956 and 2002 is basically synchronized,but it has changed in the period of 2003-2017,and the flow characteristic curve changed from clockwise to counterclockwise.Though sedimentation in the TGR has been reduced sharply from 2014 to 2017,sediment siltation rate is still high(85.2%).Sedimentation of sediment d<0.031 mm which can easily flocculated takes up the highest proportion in the backwater area of the TGR(63.5%,2009-2013),In addition,a large number of sediment flocs observed in the typical river reaches suggest that there is a high probability of fine-grained sediment flocculation in the TGR.Unbalanced water and sediment transport also caused sediment erosion in the reach of Zhutuo-Qingxichang.