Research On The Temporal And Spatial Distribution Characteristics Of Non-point Source Pollution In The Upper Reaches Of Baiyangdian Fuhe River Basin Based On SWAT Model

Water is the core element of sustainable development,which is not only inseparable from the survival of living things on earth,but also affects the natural environment and social economy on which human beings depend.Although with the continuous development of China’s environmental management project,China’s water environment has some improvement,but the status of water pollution in China is still very serious.There are many factors that contribute to the seriousness of the water environment today,but the root cause is the lack of understanding and misunderstanding of the relationship between economic development and ecological environment in the early stage of social development in China.The Fuhe River Basin is located in Baoding,Hebei Province,and is the only natural river that flows through the main city of Baoding and eventually flows into Baiyangdian.Because of its unique geographical location,the surface water environment of the basin has an important impact on both the economic development of the Xiongan New Area in Baoding and the Baiyangdian restoration project.In this paper,by using the SWAT model,a model of nonpoint source pollution was built in the upper reaches of Baiyangdian Fu River watershed,and the spatial and temporal distribution characteristics of nonpoint source pollution and the pollutant output of different land use types in the upper reaches of Baiyangdian Fu River watershed was discussed based on the simulation results,and the main sources of nonpoint source pollution in the watershed was analyzed.The main conclusions of the study are as follows:(1)A model of nonpoint source pollution in the upper reaches of the Fu River basin of Baiyangdian was constructed,and the rate was determined and validated.Based on the spatial and attribute information required for the construction of the basin nonpoint source pollution model,the data were processed using ArcGis and SPAW software to build the final nonpoint source pollution model for the upper reaches of the Baiyangdian Fu River basin.Based on the multi-year flow monitoring values at Beixindian and water quality monitoring values at Jiaozhuang,the model was validated and parameterized.The final results of the rate validation meet the accuracy requirements,and the model of nonpoint source pollution in the upper reaches of Baiyangdian Fu River Basin is considered reasonable and can meet the simulation requirements.(2)Temporal variation characteristics of nonpoint source pollution load in the watershed from 2013 to 2018:the total annual average rainfall in the upper Baiyangdian Fu River basin ranged from 312.02 to 556.67 mm,and the annual rainfall was mainly distributed in the summer months of July and August,and the total rainfall in the two months accounted for about 62.72%of the total annual rainfall.Total nitrogen and total phosphorus loads are closely related to rainfall,as reflected by the significantly higher nitrogen and phosphorus loads during the high rainfall period in summer than in other months,and lower nonpoint source pollution loads during the drought year of 2014 and high nonpoint source pollution loads during the summer rainstorm in 2016.Concentrated high-intensity rainfall can bring serious nonpoint source pollution,and if the rainfall is more evenly distributed month by month during the year,the nonpoint source pollution will be more moderate.(3)Spatial variation characteristics of non-point source pollution load in the basin from 2013 to 2018:the high load area of total nitrogen and total phosphorus in the upper Baiyangdian Fu River basin from 2013 to 2014 was mainly distributed in the eastern center of the basin,while from 2015 to 2018 it was mainly distributed in the northwest direction.However,the pollution load of total phosphorus was also reflected in the location of the central urban area of the basin where the pollution load was more prominent.From the distribution of the multi-year average,some areas in Shunping County in the northwestern part of the basin have higher output of total nitrogen than other areas,followed by the central urban area of the basin;total phosphorus is a higher load within the central urban area than the surrounding area,and the southernmost area of the basin has a lower load.(4)Non-point source pollution load characteristics of different land use types:In terms of total pollution load,both total nitrogen and total phosphorus loads in the watershed mainly come from arable land,which contributes 93.83%and 46.88%of total nitrogen and total phosphorus loads,respectively;followed by high-density residential areas,which contribute 4.5%and 38.19%of total nitrogen and total phosphorus loads,respectively.In terms of the pollution load per unit area,the model simulation concluded that the pollution load per unit area for total nitrogen:construction land>cropland>highdensity residential area(urban)>grassland>low-density residential area(rural);and the pollution load per unit area for total phosphorus:construction land>high-density residential area(urban)>low-density residential area(rural)>cropland>grassland.