Study of Donghu Lake Water Eutrophication Simulation Based on Mike21

Abstract In this paper, a water environment numerical model of donghu lake is constructed based on MIKE21. Firstly, the hydrodynamic numerical model of donghu lake is established by FM module. A nonlinear triangular grid computing domain was created in the research area, initial boundary conditions and wind-driven data were set and other hydrodynamic parameters were input. The actual water level and velocity data in the part of research periods in December 2017 were used for model calibration and verification. Calibration results: vortex viscosity coefficient is 0.29 and manning constant is 0.42m1/3/s. The result of hydrodynamic simulation is in line with the actual situation. On this basis, the water quality module WQ was coupled to simulate the water quality of donghu lake. The simulation period is from November 15 to December 17, 2017.The measured water quality data on December 17 were selected for model calibration and verification, and the errors of each verification point were counted. The calculated results show that the simulated MSE of chlorophyll a concentration is 19.60%, and the simulated MSE of orthophosphate phosphorus is 25.36%. The overall simulation accuracy is well, which can reasonably show the changes of main water quality indexes in donghu lake.