Simulation Of Agricultural Non-point Source Pollution In Shanmei Reservoir Watershed Base On AnnAGNPS

With the validating control of point source pollution,the effect of non-point source pollution on the water environment is increasingly prominent.Since its own characteristics,the surveillance and governance of non-point source pollution is much more difficult.By utilizing engineering measures combined with administrative measures,the Best Management Practices(BMPs)has become a effective way of controlling and managing the non-point source pollution.ShanMei reservoir watershed is a vital source of drinking water in QuanZhou city.As the economic growth and the increase of human activity in the drainage basin recently,the agricultural fertilizer application rates,livestock industry pollution and rural domestic pollution increased markedly,which resulted Total Nitrogen went beyond the standard limit of class-V water in the ShanMei reservoir watershed.As a consequence,both the degradation of water quality and severe pollution exert a negative influence on the social development in QuanZhou city.Watershed above the dam of ShanMei reservoir is selected as the study area,based on the model calibration tool AnnAGNPS-PY,a watershed-reservoir model AnnAGNPS which stimulates the daily process of hydrodynamic and water quality of ShanMei reservoir watershed was developed.The model assessed the amount of TN analyzed and the spatial distribution of TN in the ShanMei reservoir watershed quantitatively.Furthermore,this dissertation evaluated the inhibiting effect of BMPs on non-point source nitrogen under different BMPs scenario and probed into the model parameter uncertainty's influence on the inhibiting effect.The results showed that:(1)Based on the Python tool,the automatic calibration tool of AnnAGNPS model was established with the conception of set parameters combined with Monte Carlo algorithm,which accomplished the calibration of daily runoff-sediment-yield volume and TN parameters in ShanMei reservoir watershed.The results suggested that AnnAGNPS model could successfully stimulate the daily process of hydrodynamic and the pattern of water quality.(2)There existed similarity between TN load yield distribution and spatial distribution of orchard to some extent,which the peak value of TN load located in the Huyang town of Huyang river sub-watershed and Dapu town of Tao river sub-watershed.(3)The simulation result of BMPs demonstrated that the TN cut in ShanMei reservoir watershed was affected predominantly by the nitrogen fertilizer application rates controlling treatment,while returning the grain plots to forestry and reducing farmland showed the secondary significant effect on TN cut and protective cultivation measures was the minor influential scenario.The uncertainty of model parameters would affect the magnitude of TN cut coefficient rather than change variational direction,and the model suggested that the influence of uncertain parameter was positively correlated with the TN cut coefficient addition.