Abstract: To quantify the effect of water network connection on eutrophication, we established a mathematical water eco-environmental model of the Great Donghu Lake Network as a case study. Having simulated and analyzed the variations of eutrophication indices inclusive of COD, TN, TP and Chl-a before and after water network connection, we assessed the effect of water network connection on the comprehensive trophic state index and trophic states of lakes. Our findings manifested that after the water network connection, the water quality in Yangchun Lake, Shahu Lake and Beihu Lake improved, and the algae biomass and eutrophication level decreased; whereas the water quality in the East Lake and Yanxi Lake deteriorated, and the algae biomass and the eutrophication level increased. The results indicated that the effect of water network connection on eutrophication was complex with pollution risks. The research results offer reference for the management and operation of water network connection project.

Key words: water network connection, mathematical water eco-environmental model, eutrophication, pollution risk, the Great Donghu Lake Network