近50年来荆江三口分流分沙变化研究

Research on the flow and sediment diversion in the three outlets along Jingjiang River in recent 50 years

荆江三口是联系长江干流与洞庭湖的水沙连接通道,是江湖关系调整变化的纽带。本文通过荆江三口近50年来的实测资料,对荆江三口分流分沙历年变化规律及其影响因素进行了深入的分析和研究。结果表明:三口洪道泥沙淤积、三口口门河势变化、荆江河床冲刷、洞庭湖淤积萎缩是影响荆江三口分流分沙变化的主要因素。20世纪50年代以来,荆江三口分流分沙呈逐年减小的趋势,其分流分沙比由1956-1966年的29%、35%减小至1999-2002年的14%、16%,年断流天数也逐渐增多。三峡水库蓄水运用后,荆江三口分流分沙比分别为12%、18%,与1981-2002年相比,尚未发生明显变化,除松滋口沙道观站断流天数有所增加外,太平口、藕池口断流时间也未出现明显增加或减小的现象。

The three outlets along the Jingjiang River are the waterways to link the Yangtze River and Dongting Lake. According to the measured data in the past 50 years, the change law of flow and sediment diversion through the three outlets and affecting factors are analyzed. The result shows that the variation rule of flow and sediment diversion through the three outlets is affected by the following four factors, sediment deposition in the channel of the three outlets, the river regime regulation at the entrance of the three outlets, riverbed scouring in the Jingjiang reach and the deposition and shrinkage of Dongting Lake. Since the 1950s, the diverted flow and sediment in the three outlets was obviously decreased. From 1956 to 1966, the flow and sediment diversion ratios are 29% and 35% respectively, whereas from 1999 to 2002, they are decreased to 14% and 16%, meanwhile the no-flow days increase accordingly. After the impoundment of the TGR, the flow and sediment diversion ratios are 12% and 18 % respectively. Comparing with the period from 1981 to 2002, there is no obvious change of flow and sediment diversion in the three outlets, but no-flow days at Shadaoguan station of Songzi outlet increases.