Simulation And Study On Water Diversion Scheme Of Kunming Pool(Test Section) In Xi'an Based On Hydrodynamics And Water Quality Coupled Model

Urban artifical lakes occupy a very important position in the process of urban construction and development.However,due to its unique geographical environment and poor self-repairing ability,the water environment of urban artifical lakes is poor.How to improve the ecological environment of urban artifical lakes is a major scientific problem that needs to be solved of water environment research in China.At present,ecological water supplement through artificial water sources is one of the more effective and widely used improvement measures.Based on the MIKE21 model,a two-dimensional hydrodynamics and water quality coupled model was constructed to meet the water environment characteristics of the Kunming Pool test section in Xi'an.On this basis,four kinds of ecological water diversion schemes were designed by applying the scenario analytical method.Then,the characteristics of water environment under these water diversion schemes were simulated by using the two-dimensional hydrodynamics and water quality coupled model that had been constructed.At the same time,the hydrodynamic characteristics and the diffusion law of pollutants of the Kunming Pool test section were analyzed.Finally,the improved fuzzy comprehensive evaluation method and comprehensive nutrition state index method were used to evaluate and analyze the simulation results.And then the optimal scheme was filtered to provide some references for the water management and water environment management in the Kunming Pool.The main conclusions are as follows:?1?Under the four kinds of water diversion schemes,a number of different sizes of circulation occurred near the coast of the Kunming Pool test section and near the artificial island.And under these several schemes,the distribution characteristics of the water body velocity in the lake area were all as the velocity near the shore was greater than the velocity in the center of the lake.The velocity near the shore was about 0.07⁰.09m/s,and the velocity in the center of the lake was about 0.01m/s.However,there were some differences between the hydrodynamic simulation results of these water diversion schemes:?1?under the influence of different water diversion methods,compared with the scheme 1?water diversion through one water inlet?,the scheme 2,the circulation phenomenon of the scheme 2,the scheme 3 and the scheme 4?water diversion through two water inlets?were more obvious in the western lake area of the Kunming Pool test section.?2?under the influence of different ratios of water diversion flow between the east and west inlets,the location of the circulation in the middle of the lake area of the Kunming Pool test section of the scheme 2?water diversion flow ratio is1:1?,the scheme 3?water diversion flow ratio is 2:1?and the scheme 4?water diversion flow ratio is 5:1?was shifted from the center of the lake to the west.?2?Under the four kinds of water diversion schemes,the concentration of TN,TP and COD_Mn in the water body of the Kunming Pool test section was all improved as a whole(the concentration of TN was improved by 72.58%to 76.96%%;the concentration of TP was improved by 40.45%to 43.48%;the concentration of COD_Mn was improved by 34.43%to40.25%).Among them,the improvement of overall water quality of the scheme 4 was the best,and the improvement of overall water quality of the scheme 1 was the worst.And in addition to the failure of the scheme 1 to achieve the water quality target set by the Kunming Pool test section,that is to achieve the class?water quality of the lake,the other three schemes had achieved this goal.?3?There were different effects on the improvement of water quality in different lake areas of the Kunming Pool test section under the four kinds of water diversion schemes:the improvement effect of water quality in the eastern lake area of the Kunming Pool test section from good to bad was followed by the scheme 1,the scheme 4,the scheme 3 and the scheme2;the improvement effect of water quality in the central lake area of the Kunming Pool test section from good to bad was followed by the scheme 4,the scheme 3,the scheme 1 and the scheme 2;the improvement effect of water quality in the western lake area of the Kunming Pool test section from good to bad was followed by the scheme 2,the scheme 3,the scheme 4and the scheme 1.?4?First of all,three water quality indicators(TN,TP and COD_Mn)were selected as water quality indicators.Then,the game theory was used to improve the subjective and objective weights and then the comprehensive weights were obtained.Thereby the improved fuzzy comprehensive evaluation model was established.At the same time,combined with the comprehensive nutrition state index method,the water quality of the Kunming Pool test section under the four kinds of water diversion schemes were evaluated.Finally,through comprehensive comparative anyalysis of the evaluation results of these four kinds of water diversion schemes,it was determined that the scheme 4 was the best ecological water diversion scheme to improve the water quality of the Kunming Pool test section.