Research On Calculation Method Of Water Environment Capacity And Its Application In Heilongjiang Province

With the development of economy,the problem of water environment pollution has gradually become prominent,and has become a limiting factor affecting the sustainable development of social economy in China.In order to comprehensively strengthen ecological environment protection and complete the “accelerating the determination of the red line of ecological protection,the bottom line of environmental quality,and the upper-line use of resources,and the establishment of an ecological environment allowed list”(which is “three lines and one list”),the water environment capacity and pollution of the Heilongjiang Provincial Government for the calculation of allowable emissions,the study takes Heilongjiang Province as the research object and calculates the environmental capacity of each watershed,administrative unit and control unit based on the multi-river water environment quality model,in which way to achieve refined water environment management and TMDL control in Heilongjiang Province.First,according to the requirements of the water environment quality model,the SWAT hydrological model is selected as the hydrological calculation tool.The model database was established,and then the four-level water function partition of Heilongjiang Province was used as the calculation unit.The SWAT model was used to calculate the hydrology one by one to generate of 43 basins and the generalization of river sections in Heilongjiang Province.In the process of hydrological calculation,the three types of abnormal watersheds that cannot be correctly generated by conventional methods-plain areas,boundary river areas,and areas with abnormal DEM data were corrected based on the actual conditions of each area.The results show that the three types of abnormal watersheds can correctly complete the formation of water systems after correction.Then use python to write scripts to complete the processing of the SWAT model water system generation results,and establish a river reach generalization table for each watershed.Based on the river basin generalization table of each river basin,a one-dimensional steady-state river water quality model is selected,and the calculation of the environmental capacity of 578 river segmentsin 43 basins is completed according to the distribution method based on the cumulative degradation ratio of each tributary inlet.The environmental capacity of the whole province of Heilongjiang Province was 10.915 million tons of COD and 70,200 tons of ammonia nitrogen per year.Then,the Ashi River Basin is selected as a typical watershed.Uncertainty analysis is carried out from three levels: the comprehensive degradation coefficient of pollutants(K value),the average flow of the dryest month of each month,and the environmental capacity under different guarantee rates.According to point sources and non-point sources,the river basins of Heilongjiang Province have been estimated the amount of pollutant load inflow and discharge,combined with the calculation results of environmental capacity,based on the principle of no further deterioration of water quality and compliance of water bodies,according to the comparison of pollution load and environmental capacity The small value is the maximum daily load distribution of each control unit in Heilongjiang Province,and statistics are made according to prefectures,districts and counties.Finally,from the perspective of pollution source emission reduction,specific measures for water pollutant emission reduction and water pollution prevention and control were put forward in order to facilitate local government environmental management.