Research On Water Environmental Capacity Of Typical Polluted Reach Of Yanhe River

With the rapid development of the economy and society,the water environment pollution has become more and more serious,and has become an urgent problem to be solved.Water environmental capacity,as a characteristic indicator of water environment carrying capacity,can reflect the water body's capacity to hold water.Therefore,the objective and accurate calculation of the water environment capacity is of great significance to the rational use of water resources in a region,the scientific formulation of prevention and control policies,the maintenance of ecological health of water bodies,and the realization of green social and economic development.This paper takes the Yanhe River in Shaanxi Province as the goal,comprehensively collects information on the basin,conducts comprehensive evaluation and analysis,selects the typical polluted river section?Yan'an section of Yanhe River?as the object,considers the spatial and temporal changes of pollutants and river water volume,and calculates the water environment Capacity,based on the above results,formulate reasonable reduction plans for simulation and propose targeted measures.The main research results of this article include the following aspects:?1?Through comprehensive evaluation and analysis of eight water quality indicators in the five water quality monitoring sections of the Yanhe River from upstream to downstream,it was found that the water pollution of the Yanhe River in the middle and lower reaches of the city is more serious,exceeding the water quality target;Among them,COD_Cr,NH₃-N and TP are the main pollution factors.?2?The emissions of COD_Cr,NH₃-N and TP in typical polluted river sections are 1977.61t,221.06t and 38.50t,respectively,and the proportion of non-point source pollution emissions refers to point sources.The three types of pollutant emissions vary spatially with industry and population distribution,and are mainly concentrated in urban areas and areas along the river;in general,they are in the period of high water>low water>average water.?3?Taking 2016 as the base year,considering the spatiotemporal changes of pollutant river hydrological conditions,adopting a one-dimensional water environment model,selecting appropriate calculation parameters,and calculates the water environment capacity of the target area.The ideal water environmental capacity of COD_Cr,NH₃-N and TP are 10862.10t,536.94t and 108.62t respectively.The actual water environmental capacity is affected by natural factors?river hydrological conditions,precipitation,land use status,etc.?and human factors?pollutant discharge,pollutant treatment measures,water supply projects,etc.?.The actual water environmental capacity of COD_Cris 2380.43t.However,NH₃-N and TP have no remaining water environmental capacity,and the required reductions are 710.88t and 95.55t.?4?Above three kinds of pollutants,according to the upstream input of pollutants and the discharge of the basin,eight different reduction plans were formulated and the reduction effects were simulated.Under the most stringent management conditions?upstream pollutant input reduced by 30%and pollutant discharge reduced by 40%in the basin?,the remaining water environmental capacity of COD_Crand TP were 8195.63t and 7.86t,respectively,while NH₃-N only meet the requirements after the supplementary plan is implemented,which is10.10t.In summary,the emission reduction pressure of the three pollutants is NH₃-N>TP>COD_Cr.