Study On Water Environment Capacity And Distribution Scheme In Chongqing Section Of Three Gorges Reservoir Area

Since the construction of the Three Gorges Project,it has made tremendous contributions to the comprehensive social and economic benefits of national defense,shipping,power generation,irrigation,water supply and tourism.But it has also changed the law of flood and drought of the original natural water body of the Three Gorges of the Yangtze River,making the Three Gorges of the Yangtze River change from a natural channel to a seasonally adjustable reservoir,slowing down the flow speed,reducing the self-purification capacity and deteriorating the water quality,which have affected the Three Gorges reservoir area The ecological environment of the river basin has produced many adverse effects.With the rapid development of social economy,the total discharge of water pollutants in the basin will further increase,which will inevitably further aggravate the ecological environment pressure in the reservoir area.Therefore,in order to protect the water quality safety and ecological environment stability of the Three Gorges Reservoir,it is of great theoretical and practical value to carry out the research on the water environmental capacity and total amount allocation scheme during the operation period of the Three Gorges Reservoir area.In this study,the Chongqing section covering most of the Three Gorges Reservoir area is selected as the research object,and a comprehensive survey and analysis of the water environment quality and pollution sources in the Chongqing section of the Three Gorges reservoir area were carried out.The water quality classification of the Chongqing section of the Three Gorges reservoir area was carried out by the single factor index method.The water quality of the Chongqing section of the Three Gorges reservoir area is generally good,maintaining the water quality between Class II and Class III,and the water period was slightly unstable from July to September,and all sections exceeded the standard.and the phenomenon of exceeding the standard in all sections occurred from time to time.The main pollutant exceeding the standard was total phosphorus.Under the condition of annual average water quality,the Spearman rank correlation coefficient was used to test the interannual trend change of water quality monitoring sections.The water quality change of each control section of the Yangtze River mainstream tended to be stable in general from 2010 to 2017,and the water pollution of individual sections was significantly reduced.With the economic and social development,the source of urban living pollution,the source of agricultural non-point source pollution,and the source of livestock and poultry breeding have increased year by year.For the point sources and non-point source pollution loads of various districts and counties in the study area in 2017,the non-point source pollution load is calculated and analyzed.From the perspective of spatial distribution,the point source pollution load in Chongqing's main urban area is larger than that of non-point source load,and there are abundant agricultural resources in eastern Yunnan.The non-point source pollution load is generated in a large amount,which provides a scientific basis for the development of control technology and policy measures for the Three Gorges reservoir area.Based on EFDC software,the hydrodynamic model of the Yangtze River in the Chongqing section of the Three Gorges reservoir area was selected to study the process of pollutant migration and transformation in the river.The model verification results were good,indicating that it can be used to simulate and analyze the water environment of the Yangtze River in the Chongqing section of the Three Gorges reservoir area.The Chongqing section of the Three Gorges reservoir area is divided into 17 control units,considering the influence of different reservoir operation modes on the hydrological conditions in the reservoir area,based on EFDC hydrodynamic water quality model,the response coefficients of each sewage outlet to the water quality control section during the high water level operation period,the water level regulation period and the high water level operation period are calculated respectively.According to the response coefficient,the surface water II water standard is taken as the planning target,and the linear environment method is used to solve the water environment capacity of each control unit as the management environment capacity,and a total amount control scheme based on the water environment capacity was proposed.Taking population,GDP,water resources and pollutant emissions as the main factors for distribution,considering the different weight coefficient adjustment distribution model,the initial allocation of water environment capacity,and using the Gini coefficient method to evaluate the fairness of the distribution results,when population and GDP account for the main When the factors are affected,the Gini coefficient is the smallest and the total allocation scheme is the most reasonable.