Impact Mechanisms of Canals on Hydrological Connectivity of River and Lake System Interconnection Networks

［Objective］ As newly constructed river and lake system interconnection projects, canals change the connectivity pattern of the river and lake system interconnection network. Furthermore, it affects the pathways of material, energy and risk across the network, but the mechanism by which newly constructed canals affect the the river and lake system interconnection network is not yet clear. ［Methods］ The area around Laizhou Bay was selected as the study area. The SWAT+model and graph theory method were employed to analyze the hydrological connectivity of the river and lake system interconnection network under two scenarios, with and without the canal. This was done to explore the differences in the impacts of canals on the various river basins, as well as on different types of water bodies, such as lakes, low-flow streams and high-flow streams. ［Results］ In comparison to other river basins, the hydrological connectivity of the Weihe River Basin and the Mihe River Basin is greater under the no-canal scenario, with the lowest degree of influence from the canal. The Yellow River-the Guangli River Basin and the Dagu River-the Jiaolai River Basin are influenced by the canal, and the greatest improvement is observed, with the values of betweenness centrality and closeness centrality indicators both increasing by more than 20 times. The impact of canals on the hydrological connectivity of diverse basins is largely contingent upon river network structure, the number and the location of canal connections. Low-flow streams exhibited the highest value of closeness centrality indicator, which is 3.4 times and 1.5 times the average value of lakes and high-flow streams, respectively. Lakes is the most affected by the canal, while low-flow streams are the least affected. This suggests that the lower the disturbance-resistant capacity of the water body, the more sensitive it is to the canal's response. The impact of canals on different water body types is dominated by the distance of the water body from the central water bodies of the network. ［Conclusion］ The planning of regional river and lake system interconnection networks should take into account growth mechanisms, including 'preferential attachment' of betweenness centrality and anti-'preferential attachment' of closeness centrality. This will enable a more appropriate avoidance of the risk of unintended growth in hydrological connectivity.