Simulation Of Non-point Sources Pollution In Poyang Lake Based On SWAT Model

Poyang Lake is the largest freshwater lake of China, which is faced with serious threat of eutrophication in recent years. As the point source pollution has been controlled effectively, non-point source pollution (NSP) has become the main source of water pollution. It is essential to control NSP to improve water quality in Poyang Lake.By the combination of NSP model and Geography Information System (GIS), the paper studied the simulation of NSP in Poyang Lake. The characteristic of temporal and spatial distribution of NSP in Poyang Lake was analyzed. The different land use types, the different drainage area accounted for NSP load and the identification of the critical areas of NSP were studied. The results from this study could provide useful instruction for NSP control and watershed planning.This study included six chapters, which have been separated into four parts. The first part was the first chapter, which gave a general overview of the background and the review of NSP at home and abroad. The second part included the chapter two, three and four, which introduced the general situation of the research district, data preparations for SWAT model including the SWAT model building, calibration and confirmation and so on. The third part was chapter five, which analyzed the nitrogen pollutant, the spatial distribution of phosphorus and the critical area of pollution of Poyang Lake. The last part was chapter six, which elaborated on the research conclusion and the outlook of the future research.The main study contents and conclusions are as follows:(1)The watershed NSP database for SWAT model in the study area has been established using GIS, MATLAB and other technology. GIS has been used for projection transformation, property consolidation and the basin boundary extraction. In order to develop the weather generator in SWAT model, PCPSTAT software was adopted for the meteorological data statistics. The interpolation method was used to make the soil grain size conversion, and the process was realized through MATLAB program. The soil water characteristics were estimated by the SPAW program to build up soil property database. Using statistic method and field investigation, the other attribute data were obtained, such as point source pollution data, etc.(2)The SWAT-CUP program and the measured data were used to calibrate and verify the SWAT model. The results show that the application of SWAT model to Poyang Lake about nitrogen and phosphorus to study NSP is feasible.(3)The time variation of the non-point source pollution and precipitation patterns is consistent, and distribution of pollution load shows the irregular shape of M. Precipitation is not the decisive factor of NSP. The precipitation of some sub-basin was not much, but due to the combined effect of land use, slope and other factors, the loss of non-point source pollution load is huge.(4) Non-point source pollution mainly distribute in the Nanchang and Jinxian area, which accounted for about35%of the study area and there is slightly larger than the other regions, the main reason of which:the dense population of the area, livestock and poultry, arable land and low forest cover.(5)The impacts of land-use changes on NSP were evaluated. The AGRL (farmland) contributes the largest part of NSP loading whereas the NSP loading from FRST (woodland) is the least. Whether it is the contribution of the total or per unit area production volume is so.(6) The critical areas of nutrient loss were identified. The results show that the nitrogen load in this region far exceed quota, and the density of nitrogen was more than2mg/L, and the high concentration areas are mainly concentrated distribution in Nanchang, Jinxian, Yugan, Duchang and so on, which were the key area of nitrogen pollution.