The Application Of AnnAGNPS Model In Non-point Source Pollution Control In Siling Reservoir Watershed

Siling Reservoir is an important drinking water source for Yuhang district in Hangzhou city. However, water quality of Siling Reservoir deteriorates gradually and eutrophication becames the main problem in recent years. Agricultural non-point source pollution is one of the main reasons for water quality deterioration. Therefore, it is essential to carry on effective measures to reduce export loading of nutrients from agricultural non-point source. By using annual agricultural non-point source model (AnnAGNPS), the spatial distribution characteristics of non-point source pollution in Siling Reservoir Watershed were simulated, the law for nitrogen and phosphorus loss was discussed and agricultural management measures of main land use type (bamboo) were analyzed in the paper. The main results were as follows:(1)The database for AnnAGNPS in Siling Reservoir Watershed was established by data collection and field survey. According to sensitivity analysis, the model was calibrated and verified. The result showed that AnnAGNPS accurately simulated runoff with some uncertainty appearing on nitrogen and phosphorus loss simulation. The error of model was in the reasonable range, so AnnAGNPS model was fit for application in Siling Reservoir Watershed after validation.(2) In the study area, the export loading of nutrients in unit area were higher in southern and western regions and lower in northern and eastern regions. The phosphorus loss was less than nitrogen loss. Land use types had an effect on loss quantity and forms of nutrients. Forest land was the main export source of nitrogen loading with contribution rate as high as 94.18%, and orchard ranked secondly. Particulate nitrogen was the main form of nitrogen loading for cultivated land, while dissolved nitrogen was the main form for residential land, orchard and waters. The loss amount of dissolved nitrogen and particulate nitrogen was roughly the same in forest land. Forest land was the largest source of phosphorus loading, and residential land was the second. Particulate phosphorus was main form of phosphorus loss for cultivated land, orchard, forest land and residential land, and dissolved nitrogen had the dominant position only in waters. (3) Three fertilizer practices such as CK (no fertilizer), SSNM (site-specific nutrient management) and FFP (farmers' fertilizer practice) were used in the scenario analysis. The research results showed that comparing with FFP, the reduction of SSNM in dissolved nitrogen (DN), particle nitrogen (PN), dissolved phosphorus (DP) and particle phosphorus (PP) was 8.17%,4.33%,9.08% and 1.02%, respectively. The promotion and application of this technology can prevent water quality deterioration to a certain degree, and have a positive effect on improving and enhancing the environmental quality of Siling Reservoir Watershed.