A network model can be defined as a line graph which is composed of links representing linear
channels of flow and nodes representing their connections [3]. For the drainage network model, a planar
network (i.e. lines intersect only at nodes) is assumed.
For the stream network model established for this study, the network elements including links, nodes
and centers are defined. Links are channels of flow and they are connected to each other at nodes and are
the basic elements of a network. Nodes are end points of links and they represent the drain intersections.
Centers are special nodes that represent points of collection of flows (e.g. the location of a reservoir or
dam through which water flows into a river or another drain). The Huaihe River Basin network model has
established as Fig. 2. In this network model system, there are totally 211 links (channels), 213 nodes
(intersections) and 61 centers (water projects, such as reservoirs or dams).