荆江河段地形变化对洞庭湖水文情势的影响

Influences of topographical change of Jingjiang reach on hydrological situation of Dongting Lake

基于实测数据分析了荆江河段冲淤变化特征,采用数值模拟方法定量分析了三峡水库建库前后荆江河段地形变化对2008—2018年8—11月洞庭湖水文情势的影响。结果表明:荆江河道地形变化导致洞庭湖区8—11月水位下降,地形变化对洞庭湖区水位的影响程度随着与城陵矶距离增加而减弱;荆江河段和三口洪道冲刷下切削弱了长江与洞庭湖的水力联系,导致同样来水条件下荆南四河入湖和城陵矶出湖水量减少,从而间接降低了洞庭湖的调蓄能力;在枝城站来水一定的条件下,荆南四河分流量减少导致沙市—螺山河段的流量增加,同流量下螺山站中低水水位有一定的抬高。

Based on observed data,the erosion and deposition characteristics of Jingjiang reach of the Yangtze River were analyzed,and the influence of topographical change of Jingjiang reach after the construction of the Three Gorges Reservoir on the hydrological situation of Dongting Lake from August to November,2008 to 2018 was analyzed using the numerical simulation method.The results indicated that the topographical change of Jingjiang reach led to the decrease of water level of Dongting Lake from August to November,and the influence on the water level of Dongting Lake decreased with the increase of the distance from Chenglingji station.The erosion in Jingjiang reach and flood diversion channels of three outlets weakened the hydraulic connection between the main stream of the Yangtze River and Dongting Lake,leading to the decreases of water flowing into the lake from Jingjiang reach and flowing out of the lake through Chenglingji station,thus indirectly weakening the regulation ability of Dongting Lake.With a certain amount of water inflow at Zhicheng station,the decrease of water diversion to Jingjiang reach led to the flow increase in the reach from Shashi to Luoshan,and the water level with low and medium water inflow at Luoshan station rose to a certain extent under the same discharge.