Water Environment Dynamics Simulation Technology Research Based On EFDC-Danjiangkou Reservoir As An Example

Analyzing and evaluating for lake reservoir water environment situationreasonably and thus ensure its effective governance, it can plays a crucial role on thesustained, healthy and stable development of the social economy. As the water sourceof the PRC South to North Water Project, water quality standards of the DanjiangkouReservoir concerns the health of residents who live along the water mains. This paperselect Danjiangkou Reservoir as the research object, and set up the hydrodynamic andwater quality simulation model or the Danjiangkou Reservoir in2012based on thecurrent environment hydrodynamic model EFDC(Environmental Fluid DynamicsCode)which has been widely used now and analyze the hydrodynamic and waterquality changing rules according to the results of simulation.This paper firstly describes the new trends in research of the Water EnvironmentSimulation and development of Water Environment at home and abroad, and thendescribes the natural and geographical conditions of the Danjiangkou Reservoir waterand the environmental problems which exist now. Then according to the corealgorithm of EFDC for this simulation, the algorithm principle and structure areintroduced in details, and according to the structure of the input and output files,establishes the pre-processing and post-processing programs which correspond withuser’s habits, then set up the three dimensional water ecosystem which is suitable forLake Reservoir area. Danjiangkou Reservoir two-dimensional hydrodynamic model isof high simulation accuracy, the water level simulation of daily average deviation in0.1%, the results show that the thermal stratification exists during the time of wholeyear.The water temperature difference in vertical is lower at spring, is largest insummer. In autumn, the cold water on surface settles down and strengthens thevertical mixture, and this phenomenon is disappearing in winter, the watertemperature in all vertical layers remains equally. The simulation results of the flowfield shows that, the flow field in Danjiangkou reservoirs is significantly influencedby wind stress. You can see the vortex caused by the turbulent effect; the water velocity is bigger in both sides of the reservoirs, and small pattern among them.Water flow below the surface is complicated.This paper selects the dissolved oxygen, ammonia nitrogen, total nitrogen, totalphosphorus and other commonly used indicators as the research object. From thesimulation results we can find that the dissolved oxygen concentration is greatlyinfluenced by the water temperature, it presents a clear negative trend. In winter thedissolved oxygen concentration is higher than that in winter. And concentrationstratification exists at the same time, the surface is higher layer than the bottom. Theammonia nitrogen also has seasonal cycles and stratification. For total nitrogen themain factors which influence the concentration change is the algae growth andexogenous water into the reservoir. Finally using the method of multiple regressionanalysis respectively on the influencing factors for dissolved oxygen and ammonianitrogen concentration, it is concluded that the size of the influencing factors ofsorting, and then using the parameter sensitivity analysis of the factors influencing theconcentration of ammonia nitrogen parameters is done.