Study On Water Environmental Capacity Calculation Based On MIKE11 Water Quality Model

Based on the analysis of the hydrodynamic and water pollution characteristics in the GUO River Basin of the project of leading water from Yangtze to HUAI River,the water quality model?HD?,the rainfall runoff module?NAM?and the convective diffusion module?AD?of the MIKE 11 water quality model were used to establish the water quality model,Used to grasp the river COD and ammonia nitrogen distribution.MIKE 11 model combined with dilution flow ratio m value method to calculate the dynamic water environment capacity,and the river point source interception,sewage plant upgrading and other programs to improve the water quality improvement forecast..The main contents of the study and conclusions are as follows:?1?The NAM module of MIKE 11 model is used to establish the rainfall-runoff model of the study area,and the HD module and the NAM module are coupled to calculate the water depth and flow rate of the study section in 2013.The maximum water content of the surface water storage layer,Convergence time and river bed roughness and other parameters.The model uses the measured data of the GUOYYANG gate and the MENGCHENG gate to determine the parameters of the model.The results show that Re,R² and E_ns of the water depth are 3.30%,0.990 and 0.984,respectively.The Re,R² and E_ns of the flow are 9.8%,0.969 and 0.997 respectively.The simulation error of the model is small,which can provide more accurate hydrodynamic conditions for the study of river water quality simulation.?2?Based on the hydrodynamic conditions calculated by HD and NAM modules,the AD module is used to simulate the water quality,input longitudinal diffusion coefficient and attenuation coefficient.The model uses the measured data of YIMEN Bridge and YUEFANG Bridge to determine the parameters of the model.The simulation results show that the COD simulation error of the section of YIMEN Bridge is 13.7%and the ammonia nitrogen simulated error of the section of YIMEN Bridge is 14.7%.The COD error of the section of YUEFANG Bridge is 14.2% and the ammonia nitrogen simulated error of the section of YUEFANG Bridge is 16.1%.The simulated values of the contaminant concentration simulated by this model can reflect the actual variation.?3?The study of MIKE 11 model combined with dilution flow ratio m value method to calculate the river water environmental capacity.The MIKE 11 model is used to calculate the concentration of water pollutants upstream of the unit.The MIKE11 water quality model and the m value method are used to calculate the dynamic waterenvironment capacity of the river.The calculation results show that it is feasible to calculate the environmental capacity of the water quality model based on the MI value of the MIKE 11 water quality model.Compared with the traditional one-dimensional model,this method shows a significant dynamic change.It is concluded that this method is feasible to analyze the dynamic characteristics of the environmental capacity of the non-tidal river water in the cross-section.?4?The water quality model constructed by MIKE11 is used to predict the effect of point source pollution control.The result showed that sewage interception would be the most effective way to improve the water quality,which could decrease COD concentration about 18.9% to 36.8% and ammonia nitrogen concentration about 13.9%to 26.3%,respectively.In the other hand,increasing practical treatment capacity could reduce COD concentration about 15.0% and ammonia nitrogen concentration by 10.8%.Combined control measures were better than a single measure.A comprehensive plan including sewage interception,upgrade of wastewater treatment plant effluents and increasing practical treatment capacity,could reduce the COD and ammonia nitrogen higher than 86%,and the water quality of the river achieved below the Class IV surface water standard of China?GB3838 2002?.This study can provide reference and basis for river comprehensive management project decision.