| Owing to ice melting in spring the rivers in North China enter the spring flood,when the water level, water depth and flow field of the rivers change greatly, affecting water environment management, protection and utilization of water resources. At the same time, the non-point source pollution load and impact on river basin water environment management and protection of water resources. Establishing a mathematical model to realize the numerical simulation and researching river evolution law to guide the river water environment protection has become the focus in the field.Based on EFDC model, the thesis takes Songhua River in Harbin as a research object,and through which build the hydrodynamics and water quality model of Songhua River has been established in this thesis according to the hydrology and water quality monitoring data.DEM images were vectorized by using ArcGIS 10.0. The orthogonal curvilinear coordinate grids of the study area were setup by the RGFGRID program of Delft3 d software. In this paper, a two-dimensional mathematical model of the Harbin Section of the Songhua River was established by using EFDC model. The hydrodynamic condition in different time and space of the section between October and January in 2014 were simulated, and the data measured in Harbin Hydrological Station was used to verify the simulation results. The maximum difference between the simulated and measured water levels was 0.33 m with a relative error less than 10%. This model can simulate the river′s ice changing with time and space, so as to simulate and predict the hydraulic condition.Constructed on the basis of the hydrodynamic model of water quality model, the COD and NH3-N as the main simulation index of model parameters calibration and verification. Verification results showed that COD and NH3-N in three section of the average error, average absolute error, relative error, root mean square error, the average relative root mean square error were 0.547, 0.989, 5.013%, 1.169, 19.302% and-0.043,0.1, 16.951%, 0.128, 14.482%.Based on snowfall is increased by 20%, 40%, 60%, three scenarios, ice and snow melt period of whole river COD concentration between 18.67 to 21.29 mg/L,respectively, between 18.71 to 21.65 mg/L, and between 18.75 to 22.04mg/L, between0.39 to 1.18mg/L, between 0.41 to 1.39mg/L, between 0.45 to 1.62mg/L. Based on snow melting temperature increase 3℃ and 6℃ respectively two scenarios of COD and NH3-N maximum concentration respectively is hovering around 21.89mg/L and21.89mg/L, 1.72mg/L and 2.01mg/L. The blizzard snowfall is higher than 65 mm, each section of COD concentration is higher than 20mg/L for four types of water quality, and showed a trend of accelerated. When blizzard snowfall is higher than 83.4mm, in addition to the upstream, the rest of the cross section of NH3-N concentrations higher than 2 mg/L to the five types of inferior water quality. |
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