基于SWAT模型的农业面源污染尺度效应研究

non-point source pollution distributed hydrological model, which was applied to Liantangkou basin, was used to simulate and analyze the scale effects of nitrogen and phosphorus losses under current condition and different scenarios by dividing seven nested scales from upstream to downstream. The results showed that the greater nested scales were, the greater pollutant emissions per unit area discharge. The reason for that was the proportion of rice fields' area as the main source of nitrogen and phosphorus emission in the whole research area were growing. Therefore, when the proportion of rice fields' area remained unchanged among different spatial scales, the pollutant emissions per unit area were decreased because of the reuse of drainage water and removal of nitrogen and phosphorus pollutants. The simulation results under different level years and different fertilizing systems showed the same scale effects as mentioned above. What's more, the pollutant emissions at the dry year was the lowest and the emissions per unit area declined when the farmland fertilizer amount reduced.