基于图论与层次分析法耦合的荆江水系连通性评价

Water system connectivity evaluation of Jingjiang River based on the coupling of graph theory and analytic hierarchy process

近年来长江荆江河段冲刷下切严重,导致荆江三口分流入洞庭湖的水量急剧减少,使得长江与洞庭湖的江湖关系发生了变化。为了分析荆江水系连通性变化过程,首先根据研究区域的水系结构形态建立河网图模型;然后将河道(湖库)连通性综合评价函数值作为河网图模型中连通通道边的权重,构建加权邻接矩阵和畅通度矩阵;最后利用Matlab等工具计算整个水系的连通度。研究结果表明,1955—2015年荆江水系连通性整体上有增加的趋势;荆江干流河道的连通性函数值在1972年前变化不大,1972年后呈增加的趋势;而三口通道和洞庭湖的连通性函数值在2003年前逐渐减小,2003年后呈增加趋势。另外,从河道冲刷、分流分沙、湖泊萎缩等角度分析了连通性变化的主要原因,并从加强水库群优化调度、开展河道整治、实施湖泊治理等角度给出了荆江水系连通性的治理建议。

In recent decades,channel erosion of the Jingjiang River is very serious and the water quantity of the three outlets of Jingjiang River flowing into Dongting Lake has decreased sharply,which has changed the relationship between the Yangtze River and Dongting Lake.In order to analyze the change process of Jingjiang River system connectivity,this paper first establishes a river network model according to the water system structure of the study area.Then,the comprehensive evaluation function value of river(Lake and Reservoir)connectivity is taken as the weight of connected edges in the graph model,and the weighted adjacency matrix and patency matrix are constructed.Finally,the connectivity function of river network is calculated by MATLAB and other tools.The results show that the connectivity of Jingjiang River system has an increasing trend from 1955 to 2015.In addition,the connectivity function value of Jingjiang River is basically unchanged before 1972,and gradually increases after 1972.However,the connectivity function value of the three outlets channel and Dongting Lake decreases first,and then increases after the Three Gorges Reservoir impounded in 2003.Then,the reasons for the change of water system connectivity are analyzed from the aspects of channel erosion,diversion of flow&sediment and lake shrinkage.Further,this paper puts forward some suggestions on the connectivity management of Jingjiang River system from the perspective of reservoir group optimization,river regulation and lake regulation,etc.