Application Study Of SWAT On Non-Point Pollution In Hilly Area Around Taihu Lake

Nowadays, agricultural non-point source pollution is the most important factor for water environmental deterioration and lake eutrophication in China. Therefore, it's very significant to control agricultural non-point source pollution and protect our ecological environment for realizing the harmonized development of resource, environment and agriculture in China.As a typical agricultural watershed in hilly area around Taihu Lake, a little watershed of Meilin in Yixing City was selected for experiment in situ. The transportation characteristics of many forms nutrients drived by rainfall-runoff of the whole watershed were studied by field observations and lab test. Furthermore, regression relationships between daily transporation fluxes and daily runoff fluxes were set up. Then temporal variation of agricultural nutrients concentration under storm rainfall condition was analyzed.SWAT model developed by USDA Agricultural Research Service (ARS) is used to estimate the non-point source pollution. Maps, weather, properties of soils, landuse and land management data were collected for model applying. DEM of the watershed was used to define the stream network and discretize the subbasins by AVSWAT. Topographic parameters of the stream network and subbasins were also derived from the DEM. Hydrologic response units (HRUs)-the smallest computing unit of SWAT model- were defined by overlaying the land use map and soil map. Then SWAT model was calibrated with observed data. The next step was to use the calibrated parameters to calculate the daily flow, daily loadings of sediment and non-point source pollutants. In addition, daily observed flow, sediment loadings and nutrient loadings were used to validate the calibrated model. Coefficient of determination, Relative Error and Nash-Sutcliffe coefficient are used to estimate the adaptability of flow result, and coefficient of determination and Relative Error are used for assessing the result of sediment loadings and nutrient loadings. At last, the important parameters' sensitivity was analyzed. A conclusion can be drawn that the simulation of SWAT model is applicable on non-point pollution in hilly area around Taihu Lake..