Principle And Model Study Of Agricultural Non-point Source Pollution Of The Representative Polder Area In Taihu Lake Basin

As the main reason for the worse water quality, agricultural non-point pollution, which also causes soil productivity to degenerate directly, is tightly related with the hydrological process. Taihu Basin has about 14,541 km~2 polders,which take up 51% of the land area in its land plain. These polders play a pole in protecting the safety of people's lives and properties and promoting the economic development and social stabilization. However, due to the accumulation of fertilizer and pesticide in soil and the eluviations of salinity, water quality of these polders changed to be worse, the entironment was influenced, and water environment here was threatened severely. For its unique hydrology, the rule of the non-point pollution of polder is particular and is very important to be studied.A typical agricultural watershed and runoff plots in polder areas around Taihu Lake were selected and experiment in situ was conducted. The transporation characteristics of various forms nutrients drived by natural rainfall-runoff were studied by field observations and laboratory testings. Regression relationships between transporation fluxes with runoff fluxes and fertilization were set up. Temporal variation of agricultural nutrients concentration under rainfall condition was analyzed also. Furthermore, different land uses in the watershed were investigated on frequency and spatial distribution characteristics of nutrients losses in surface runoff. The main reasons about significant difference of spatial distribution were analyzed and transportation fluxes of nutrients were compared between different land uses.SWAT model developed by USDA Agricultural Research Service(ARS) is used to estimate the non-point source pollution. It is a continuous and distributed model. It is an attempt to use it in the polder around Taihu basin.Predict the impact of land management practices on water, sediment and agricultural chemical yields in large complex watersheds with varying soils, land use and management conditions. Daliy data series of May 18th to Oct 31th of 2006 were used to calibrated correlative parameters. The precision of the SWAT model is fairly good.