Simulating the Effect of Reducing the Non-point Source Pollution by Buffer Zone with SWMM

Buffer was lately found efficient in reducing and storing non-point source pollution to improve the water quality of both surface runoff and drain outflows. While the importance of reducing the non-point source pollution is gaining recognition in contemporary buffer zone management strategies, it is rarely recognized that different patterns of buffer zone are often diverse in their functions. Based on SWMM, we studied the reducing effect of paddy field with different width and planting density. SWMM is based on city's water and land management which is suitable for this case. Removal rate was used to show the effect and we established two relationships: one is between width of paddy field and removal rate, another is between slope and removal rate. The model's performance was evaluated by comparing the observed and simulated total nitrogen (TN) and total phosphorus (TP) concentrations in surface runoff. The result shows that TN and TP concentrations significantly decreased as ground water flowed through the paddy field. Using this methodology, we can not only make the discipline that how paddy field reduce the non-point source pollution obvious, but also show a successful pattern of buffer zone which is helpful for framing BMPs.