三峡水库蓄水后荆江三口分流比估算

笔者根据近50年来的实测资料，分析了三口分流比变化的原因．在1955-1990年期间三口分流比递减，主要原因是荆江河段水位下降以及三口口门淤积；而在1990-2004年期间三口分流比基本变化不大，主要原因是荆江河段水位以及三口口门冲淤均变化不大、三峡蓄水以后，长江干流含沙量将会大幅度减少，笔者结合三峡蓄水以来的实测数据预测了蓄水20年后荆江河段的水位变化．在此基础上，计算了三口口门冲刷深度以及分流比的变化．结果表明，荆江河段中、高水位下降幅度有限，三口口门河床高程下降幅度较大，因而三口分流比将不会减少．

Estimation of Flow of Three Diversions in the Jingjiang River After the Operation of the Three Gorges Reservoir

According to the field data in the last 50 years, reasons for the changes in the flow of the three diversions were analyzed. During 1955-1990, the flow of the three diversions reduced because of the water level drop in the Jingjiang river and the deposition of the three outlets ;while during 1999-2004, the three diversions changed little because the water level in the Jingjiang river and the deposition of the three outlets both changed little. After the operation of the three Gorges reservoir, the sediment discharge of the Yangtze main stream has greatly decreased. Measured data were used to predict the changes of water level in the Jingjiang river if the Three Gorges reservoir is operated for 20 years. Based on this, we estimated the scour depth in the three outlets and the changes of the flow of the three diversions if the Three Gorges reservoir is operated for 20 years. Results show that the decrease of medium and high water level is finite in the Jingjiang river, while the riverbed elevation of the three outlets drop largely. So the diversion ratios will not be reduced.