Application Of The Soil And Water Assessment Tool To Evaluate The Non-Point Source Pollution In The Westlake Watershed

The surface runoff is one of the main sources of non-point source pollution in West Lake. In order to understanding the non-point source pollution status of the Westlake Watershed, the characteristics of nitrogen and phosphorus losses by rain off-runoff of the whole watershed were studied by field observation and leb test. Furthermore, the SWAT model was used to simulate the4 main rivers in the Westlake Watershed. Provide theoretical basis for the non-point source pollution control in the Westlake Watershed.(1)TN and TP Site Meancon Centration(SMC) in runoff were positively related to rainfall intensity and were 0.24,0.14, 0.13, 0.19 mg·L-1 and 5.04, 4.59, 5.83, 5.21 mg·L-1 with rainfall applied under light rai, moderate rain, heavy rain and rainstorm respectively. The proportion of storm event in the event of a significant flow of rainfall events in the proportion reached is 32%,in which the SMC and SMA were high.(2The runoff have the positive correlation with rainfall duration and rainfall, which is0.903 and 0.786.The forest land of this three runoff plot had the significant sediment yield, while the tea garden was lattle. The pollutant concentrations in tea plantation were significantly higher than that of forest land, and the highest total phosphorus and total nitrogen reached 3.41 and32.86 mg ·L-1respectively. Compared with wood land runoff plots, the loss of total phosphorus,soluble phosphorus, total nitrogen, nitrate nitrogen and ammonia nitrogen in the two extreme rainfall events in the tea garden area accounted for 0.65, 0.57, 0.58, 0.54 and 0.58, respectively.(3)The ArcGIS software is used to calculate the spatial data, land use map, soil type map,etc., and the SPAW, DEW, PCPSTAT, MATLAB programming and other software are used to calculate the SWAT model underlying databas.(4)The model parameters are calibrated by SWAT_CUP software and the SWAT model can simulate the NPS in WestLake Watershed. The NPS mainly occurred in the rainy season, the total nitrogen output was 3478 kg(July), the maximum total output value was 951 kg(June), and the total output was 20.27% and 37.47%, respectively. The NPS mainly occurred in 5-9 months.Comparison of 4 small watersheds, the output flux of total nitrogen and total phosphorus in Jinsha River is the largest stream, which had the 54.89% and 42.14%, respectively, of total flux.THE key areas of the comprehensive analysis of total nitrogen and total phosphorus loss, Chang qiao stream of small watershed and the southern of Long HongJian small watershed were key areas of NPS for the Westlake Watershed.