SWAT-Based Simulation On Non-Point Source Pollution In The North Watershed Of Miyun Reservoir

In order to manage and control effectively Non-point source pollution (NPS) in watershed, it is necessary to simulate the NPS process at temporal and spatial scale by the combination of NPS Model—Soil and Water Assessment Tool (SWAT) with Geography Information System(GIS) and Degital Elevation Model(DEM), and analyze the variartion to provide the valid instruction for control and manage NPS.This paper reviews the development of NPS Model. As a case study, the SWAT model was applied to simulate the NPS loading of North watershed of Miyun reservoir, The main contents and research results are as follows:(1) The watershed NPS basic database for SWAT model in the study area has been established using the GIS and Visual Foxpro6.0 technology. According to the watershed spacial parameterization and discretization, the auto-evaluation of model run units (Hydrologic Response Units, HRUs) were solved; by the grading spatial relationship analysis, the HRUs were routed upwards and the spatial integration of the simulation results were gradually realized.(2) The model simulations are affected greatly by parameters loss derived from DEMs with different resolutions, especially in the slope. As an example of Mangniuhe River watershed in Miyun reservoir, error control on the value of slope deriving from different precision DEM is madeusing the curve estimation regression method to build the equations of slope losses?.(3) Based on DEM, study area was depicted as 75 sub-basins and 114 HRUs. The simulation of NPS runoff of the watershed is carried with corresponding data of three years (2000～2002) by SWAT. Also the results are analyzed from space and time (annually and monthly?) respectively. On the time scales, the watershed of Baihe River icontributed more NPS loading . Distribution of Organic-N and organic-P load shows a pattern of "high in west-- low in-Middle and - high in East"; On the space dimensions, NPS loading is contributed mostly during the rainy season (Jun.～Sept.). Distribution of Organic-N and organic-P load shows the temporal shape of "W". comparison with five different land-use manners in watershed, the impact of land-use changes on sediment are evaluated. For organic-N...