Application of AnnAGNPS in Upper & Middle Watershed of Guilin Taohuajiang River in Karst Area

Abstract-The 3 themes DEM·Soil.shp and Field.shp required by AnnAGNPS are prepared by MapGIS 6.5, ENVI 4.0 and ArcView GIS 3.3 through data transformation. These data layers generated the spatial data and themes that are used in AnnAGNPS, they are executed finally as soon as the parameters used in AnnAGNPS are calibrated. The simulated values of total nitrogen and phosphorus are 27.5 t/a and 8.03 t/a and the observed values are 31.06 t/a and 10.43 t/a respectively. The scale error values are 11.5% and 23% respectively. They are all underestimated because of the fast use change format. The error of simulated values of nitrogen and phosphors are acceptable. The simulated results show that AnnAGNPS can simulated transport and loss of the nutrients in small river watershed in karst area.