The Research On Water Environmental Capacity And Non-point Source Pollution Simulation Of Tiaoxi Watershed Using SWAT And WASP Model

Non-point sources pollution has become a serious environmental problem in the world. One of the key management skill to solve the problem of non-point source pollution is based on total water pollutants capacity control in watershed scale. In this paper, SWAT and WASP model applied to simulate non-point source pollution and water quality of Tiaoxi watershed in Zhejiang Province, accounting target pollutants’ water environmental capacity. WASP model simulated nitrogen and phosphorus and other pollutants in the main rivers of Tiaoxi watershed, and to explore the response relationship between the water environment pollution and water quality, and to determine the main pollution control river. According to estimates of water environment capacity, the capacity and emission reductions are allocated to provide a scientific basis for the total non-point source pollution control on Tiaoxi watershed. The main contents and results are as follows:(1) Building the spatial database of Tiaoxi watershed using ArcGIS and simulating the non-point source pollution of Tiaoxi watershed based on the SWAT model. According to the result of verification the runoff of Pingyao site, calibration and validation of the monthly average runoff R2respectively0.89,0.88, Ens are0.84, it can be known that SWAT model can effectively simulate the hydrological cycle status of Tiaoxi watershed. According to the SWAT model simulation results, the spatial distribution of ammonia nitrogen, total phosphorus and total nitrogen pollution load showed that the non-point source pollution loss load per unit area in the eastern part is greater than the west, and central regions was relatively low. And the spatial distribution character of various pollutants was quite similar.(2) Based on the results of SWAT model simulation, each sub-basin scale pollution load and monthly flow output input into the WASP model, and to achieve the combination of SWAT and WASP model, simulating the main river water quality in the Tiaoxi watershed. The results showed that the simulation of non-point source pollution and water quality was successful. Non-point source pollution load was consistent with its river water quality, and the pollution of east part was poorer than the west part.(3) Non-point source pollution is the major pollution source of Tiaoxi watershed.Under different rainfall conditions, the amount of non-point source pollution into the river was changed. So under the hydrology guaranteed rate of90%, the dry period (January-March), the wet period (July-September) was chosen to calculate water environmental capacity. The results of water environment capacity calculation indicated that most river in Tiaoxi watershed was excessive emissions, and TN%TP water environmental capacity of water were quite different during the different periods. The reduction amount of each pollutant is calculated, according to the upper and lower limits of water environmental capacity. The result shows the whole watershed ammonia dry season, wet period reductions were1311.31t/a,1088.46t/a; TN were3499.58t/a,3004.62t/a; total phosphorus were354.59t/a,311.57t/a.