Study On Pollutant Carrying Capacity And Total Amount Control Based On SWAT Model In Wuhan Section Of Fuhuan River

The calculation of pollutant carrying capacity is a key step of the total amount control of pollutants and water environment management.However,the general mathematical model method is widely used to calculate the pollutant carrying capacity of water bodies in China.There are many shortcomings in the process of implementation.Firstly,the hydrological conditions are relatively simple,which cannot reflect the dynamic change of the river's pollution carrying capacity.Secondly,in the calculation process,we tend to focus on the control of point source,and the quantitative estimation method of non-point source is too simple.Thirdly,empirical formulas are often used in the design of hydrological conditions and the selection of parameters in basins where data are scarce,and the calculation results are highly uncertain.As the main sewage river in Wuhan,the Wuhan section of the Futun River has accepted a large number of point source and non-point source pollution loads from the upstream and this section,which has far exceeded the pollutant carrying capacity of the river itself.Therefore,it is of great practical significance to carry out the pollutant carrying capacity of Fuhuan river in wuhan and the total quantity control of pollutants in a river basin.In this paper,various means such as data collection,field investigation and literature review were applied in building basic database in the Fuhuan river basin with the help of ArcGIS.And then,the SWAT model was employed to implement hydrological and water environmental simulations.Based on SWAT model,the Fuhuan river basin of space-time distribution features of agricultural non-point source pollution are analyzed;Based on the SWAT output,the carrying capacity of Fuhuan river in normal and dry periods was calculated.The maximum daily load of pollutants in representative section of Fuhuan river was analyzed by using Load Duration Curve,and the monthly characteristics and seasonal variations of total maximum daily load were also analyzed,and finally the pollution load distribution plan was formulated.The main conclusions are as follows:?1?the investigation of pollution sources and the calculation of sewage discharge in Fuhuan river show that:for NH₃-N,the contribution of urban domestic pollution in point source is greater,and that of agricultural fertilizer pollution in non-point source is also greater;For TP,agricultural fertilizer pollution was the main source.?2?based on SWAT model,the hydrology and water environment model is established in Fuhuan river watershed.The runoff parameters of the model were calibrated and verified by using the existing water quality data of hydrological stations and outlet sections.The results show that the model simulation results are to be believed and can satisfy the accuracy of runoff and water quality simulation in study area;runoff,sediment and non-point source load are strongly correlated with each other in time distribution.The spatial distribution results showed that the regions with high non-point source pollution load were mainly located in the areas with large cultivated land and forestland area such as dongxihu district and huangpi district.?3?based on a one-dimensional water quality model calculation of different phase of water environmental carrying capacity in Fuhuan river area,the results shows that:the pollutant carrying capacity fluctuates greatly in both normal and dry periods,for NH₃-N,the pollutant carrying capacity of the water functional area calculated under the hydrological conditions in the high water period is 1.8 times higher than that in the low water period;for TP,the pollutant carrying capacity of water functional area calculated under hydrological conditions in high water period is 1.69 times higher than that in low water period.?4?The maximum daily load of pollutants in river section based on load duration curve shows that the pollutant carrying capacity fluctuates greatly throughout the year due to the change of discharge,the maximum daily load of pollutants was the highest in zhujia estuary;each section has a higher daily load carrying capacity in the high flow season and summer.?5?Based on the calculation of maximum daily load of pollutants in river section,the outlet section of the basin is taken as the total control object,and the impact of upstream inflow is taken into account when pollutants are distributed.The results show that:Non-point source pollution load proportion in Fuhuan watershed,the largest annual point-source allow2711.77 t load of NH₃-N,TP 202.38 t,Jiangan district,Jianghan district,Qiaokou district with high urbanization rate have been the point source allows more load;the average annual allowable load of non-point source was NH₃-N 2090.8874t and TP 890.2t.Due to the large area of cultivated land and forest land,the allowable load of non-point source was distributed in Dongxihu district and Huangpi district.