| With the acceleration of the process of urbanization in cities and the rapid development of social economy,the problem of urban lake water pollution has become increasingly serious.Wuhan Donghu Lake is a representative shallow lake in the middle and lower reaches of the Yangtze River.With a large amount of nutrients and waste water entering the water body,the water quality of Donghu Lake deteriorates and the eutrophication becomes worse.Since the Donghu Lake water system is increasingly divided into many sub-lakes by dikes,the water systems of the sub-lakes Blocked by a large number of bridges and culverts,the circulation of the Donghu Lake water system,which originally had poor circulation,became worse and the hydrodynamic conditions were extremely poor.This study analyzed the sources of pollutants in Donghu Lake,including point source pollution,non-point source pollution,dustfall into the lake,and endogenous pollution,and analyzed the characteristics of pollutant concentration changes under various pollution pathways.The MIKE 21 two-dimensional hydrodynamic water quality model was used to analyze the relationship between water system connectivity and the Donghu Lake water quality response in the Donghu Basin.The established model was used to simulate and analyze the changes in the water quality of Donghu Lake under different operating conditions in order to provide some reference values for the Donghu Lake water environment treatment planning.The main research content is as follows:（1）The sources of pollutants in Donghu Lake mainly include point source,surface source,internal source and dustfall.The indicators of COD,NH3-N,and TP in the pollution load into the lake showed higher contribution from surface sources,followed by point sources;TN indicators showed higher contribution from point sources,followed by surface sources,which were mainly affected by the sewage Impacts of tail water discharges from treatment plants and Wangjiadian Sewage Treatment Plant.（2）Through the MIKE 21 model construction and parameter calibration,the water level of the actual water level in the Donghu Lake was selected to verify the water level calculation of the hydrodynamic model.The water quality monitoring data from the five monitoring points set in the Donghu Lake were used to rate and verify the water quality model.The measured values are in good agreement and the trend of concentration change is relatively reasonable.The established MIKE 21 model can be used to simulate the hydrodynamic quality of Donghu Lake.（3）Different scenarios were set up,and the model was used to simulate the water quality improvement in the Donghu River system under different conditions.The results showed that the effect of connectivity in the Donghu Lake water system on the mean flow velocity and the average pollutant concentration was not significant.The water mobility of the Zihu flow field turbulent area connected by the water system is enhanced,and the Zihu Lake,Miaohu Lake and other sub-lakes are most affected by the internal connectivity project.The water connection project in the Donghu Lake has certain improvement effect on the pollutants in some waters at the connection site.However,the improvement effect on the whole lake is not obvious enough. |
