Temporal-Spatial Distribution Of Non-Point Source Pollution In Mei Jiang River Watershed Based On SWAT Model

With the rapid social development and the intense growth of mankind activities, Water pollution problem has become the global problem of water environment. In the point source pollution basically get better control and governance, non-point source pollution has become the main threat of water pollution. Non-point source pollution is the main cause of the surface water pollution, and to the largest proportion of agricultural non-point source pollution. Agricultural non-point source pollution formation process randomness, impact factor is diversiform, widely distributed, etc. Consequently, the research and control of agricultural non-point source pollution is difficult.Meijiang river basin in Jiangxi province as the research area in this paper, on the basis of considering natural characteristics such as terrain, soil, weather, land use, etc. SWAT(Soil and Water Assessment Tools) model was used to calculate the watershed agricultural non-point source pollution transport under the Agricultural production activity, which is red soil region under the background of subtropical monsoon climate. According to the measured data, SWAT model were adjusted to analyze the temporal-spatial distribution patterns of the non-point pollution load in the watershed. The hydrological processes and nitrogen and phosphorus nutrient loads were also calculated. Results showed that there was significant temporal-spatial characteristic in the watershed. Through research, I get conclusions as follows:(1) On the time series analysis of agricultural non-point source pollutants transport law,annual load variation: The emissions way of Nitrate nitrogen s given priority to with infiltration, contribution rate is as high as 63% in the seven years(2005-2011). This phenomenon is associated with basin high vegetation coverage. Nitrogen and phosphorus nutrient loads have obvious correlation with rainfall in the basin; monthly load variation: according to the simulation results of the 24 months in 2010-2011, organic nitrogen, organic phosphorus have almost the same change trend and has fluctuated greatly under the influence of rainfall and runoff.(2)In the analysis of agricultural non-point source pollution spatial distribution characteristics, organic nitrogen, phosphorus spatial distribution characteristics were cited subbasin as a unit in 2011. The amount of nitrogen and phosphorus leached from the subbasin has significant correlation with runoff, sediment yield. Because of the water resources of Meijiang river middle and lower reaches, runoff and sediment yield is higher in the Huangpi and Huitong rivers. So that pollution emissions are higher in this region.(3) Nitrogen and phosphorus nutrient discharge gap is very big under different land use types, the largest organic nitrogen and phosphorus pollutant emissions contribution rate is 64.8% and 65.8% of the whole valley in the cultivated land. Simulation analysis shows that Meijiang river basin has obvious spatial and temporal distribution under the actual cultivation management system and fertilization measures. Non-point source pollution load of nitrogen, phosphorus caused by agricultural production contribution rate is very high under the hydrological response unit(HRU).