太湖流域南河水系无尺度结构

Scale-free structure of the Nanhe drainage of Lake Taihu watershed

基于图论和无尺度结构视角及节点度指标初步探讨太湖流域南河水系结构的数量特征和空间秩序,为辨识和模拟流域水文情势提供重要参数.主要结论如下:太湖流域南河水系结构的数量节点度不符合幂次分布,而长度和等级节点度符合无尺度结构;南河水系结构符合Horton第一定律和第二定律,同时此类特征亦符合无尺度结构,但指数函数回归模拟的R2相比乘幂函数回归模拟的R2较低;由幂次定律所支配的这种水系网络特征状况是由地区地形、农业灌溉、圩区建设和城市化过程共同推动;从节点度角度看,南河下游圩区使得河网数量节点度增加,等级节点度和长度节点度降低.

On the base of Graph Theory, free-scale structure viewpoint and vertex degree indices, the paper describes and analyzes numeral and spatial characteristics and their urbanization relationships of drainage structure within the Lake Taihu watershed. Numeral degree of Nanhe drainage structure in Lake Taihu watershed does not accord with power function distribution, but length and rank degrees represent the characteristics of scale-free structure. Additionally Nanhe drainage structure is appropriate for not only Horton First Law and Second Law but also scale-free structure. Scale-free structure really fits a power function, which reflects an e system controlled by few gathered nodes and provides some key methods for identifying and modeling hydrology index of watershed. Lastly the power law behind the drainage structure shows the human disturbance difference exerted on drainage structure. In the highly urbanized area of Nanhe middle stream and downstream numeral and rank vertex degrees are both high, but length degree is low and in the less urbanized area, the area rank vertex degree is also very low. In the upstream area, urbanization level is low and length vertex degree is high, but rank vertex degree is low. The numeral vertex degree of most of nodes is low and has no clear relationship with urbanization.