基于洞庭湖水沙模型的荆南三河冲淤变化研究

荆南三河起于荆江河段，水沙情势受上游来水来沙条件影响较大，荆南三河冲淤变化研究有助于认识洞庭湖地区防洪形势和江湖关系的演变。本文构建了洞庭湖水沙数值模型，计算了三峡工程运行后荆南三河各河段的冲淤变化，并结合实测冲淤数据探究了影响荆南三河冲淤的因素。计算结果表明，三峡工程运行后荆南三河河道发生普遍冲刷，冲刷趋势短期内不会变化，但冲刷强度逐渐下降。三峡工程运行后，荆南三河口门分流量、分流比和分沙比均无明显趋势性变化，分沙量大幅度减小，清水下泄改变了荆南三河冲淤状态。此外，采砂对荆南三河冲淤也有重要影响。

Channel evolution of river system in Dongting Lake after Three Gorges dam based on flow-sediment model

The river system in Dongting Lake, originating from the Yangtze, has a flow-sediment regime that depends much on the Three Gorges Reservoir. A study on the scour and sedimentation in this system and its time changes can help understand the river’s flood control and the river-lake relationship. In this study, we develop a numerical flow-sediment transport model and simulate the scour and sedimentation and its changes in the river system in the period starting from the reservoir operation. The dominant factors are examined on the basis of the simulations and field observation data. The results show that in this period, a general scour has occurred over the system－a trend that will not change in the near future－but its intensity has been decreasing gradually. And no obvious change has been observed in the trends of the diverted flows, flow diversion ratios, or sand diversion ratios at the estuaries of the river system. In the period, the amount of diverted sediment has been reduced tremendously, as the flow from the reservoir is laden with much less sediment and thus has altered the scour and sedimentation conditions of the river system. In addition, sand mining has also imposed a significant impact on the river system.