A Non-Point Source Pollution Information System Based On GIS And Its Priliminary Applications In Liuxi River Downstream Watershed And ZengJiang Upstream Watershed

With the effective control of industrial and residential point source pollution, non-point source pollution has been the major factor of water pollution. The traditional ways to solve non-point source pollution are to develop statistical models at first and later to build mechanism models, which can't simulate the pollution process effectively. Since the 1990's,with the rapid development of computer technology and 3S applied in watersheds, the GIS can accurately and promptly resolve the spatial and temporal distribution of non-point source pollution according the topography and land-use change in the watershed, which the traditional models can not perform. This study tries to establish a non-point source information system to integrate GIS and AnnAGNPS , make a preliminary computing and analysis and introduce the ways of system constructing and model application using the examples of Liuxi river downstream watershed and Zengjiang river upstream watershed. The study of this paper is of great values to the watershed management especially for those places in which economy is developed and environment is worse.The result showed:1 The amount of soil loss has a direct connection to R(rainfall factor) when other factors change little .The amounts of sediment and organic carbon also have a direct connection to soil loss, because most of them are attached to the eroded soil washing into water. The total N and total P can be directly dissolved in the water, also can be attached to the eroded soil to the water. The amount of total N and total P have relationship with the amount of soil loss, runoff and fertilizer application rate, so their changes are complex .The R(rainfall factor) in Liuxi downstream watershed has the order of 2000>2002>1998, so the amount of soil loss ,the sediment and organic carbon have the same order. The total N has the order of 2000>1998>2002, the total P has the order of 2002>1998>2000,and the amount of runoff have the order 2000>2002>1998. The R, the amount of soil loss, sediment and organic carbon in Zengjiang upstream watershed have the order of 2000>2002>1998.The amount ofrunoff, total N and total P have the order of 2002>1998>2000.Because its larger R and steeper topography slope, the amounts of all the index in Zengjian upstream watershed are larger than Liuxi downstream watershed.2 The non-point source pollution are mostly distributed in the lower elevation places places, the places near the outlets, or the places which have relatively concentrated agricultural land or worse vegetation. With the larger slope , the amount of total N,. total P and total organic C have a trend of becoming larger.3 The dates of maximum of attached N, P, organic carbon and dissolved P, N in the outlets which is mostly in April-October month is same as those of maximum 24-hour rainfall. In contrast of attached N, The amount of dissolved N changes little with the change of rainfall.4 This paper not only computes the amount of pollution, but also analyses in detail the spatial and temporal distributing of the result, and discovers some preliminary laws. To reduce the non-point source pollution, we must according to the spatial and temporal distributing reduce the amount of fertilizer, improve vegetation to reduce runoff and soil loss, especially in those places liable to be polluted.