基于8场降雨事件的水量、污染物同步监测资料,根据平均浓度法计算流域出口断面各污染物负荷,并用于模型参数率定及验证,分析了流域泥沙、总氮、总磷流失的时空分布特征。结果表明:该模型在南方湿润地区适用性较高。流域内全年非点源污染负荷分布不均,绝大部分集中在汛期的4—9月; 流域总氮、总磷污染负荷空间分布较相似,流域上游东北部区域村落富集以及耕地比例较大,污染负荷较大,流域下游受人类活动的影响产污量较大; 因土地利用类型不同,单位面积污染物负荷输出差异显著,各类土地利用类型中泥沙、有机氮、有机磷、无机磷污染物流失强度由小到大依次为林地、建设用地、草地、耕地; 耕地是非点源污染流失的主要源区,实行退耕还林措施,流域泥沙、TN和TP负荷依次减少35.8%,46.1%和35.8%; 减少氮肥和磷肥施用量50%,TN和TP负荷分别减少18.1%和8.9%。因此,降低施肥量和实行退耕还林措施是控制泗合水流域非点源污染的关键,本研究可为流域生态环境治理提供一定理论依据。
Based on the monitoring data of water quantity and pollutants in 8 rainfall events,the non-point source pollution load at the outlet section of the basin was estimated according to the average concentration method,and was used to calibrate and verify the model parameters. The variation process of sediment,total nitrogen and total phosphorus in different underlying surface conditions was modeling and the temporal and spatial distribution characteristics were analyzed. It could be seen that SWAT model was feasible in the southern humid area. The results indicate that the distribution of pollution load was uneven,most of pollution loads concentrated in the flood season covering the period from April to September. The spatial distributions of pollution loads of total nitrogen and total phosphorus in the basin were similar,the pollution load was large in the northeast area of the upper reaches of the basin where the villages clustered and the proportion of cultivated land was large. Moreover,the output of pollutants in the lower reaches of the basin is large because of the influence of the human activities. The differences of pollution load transports per unit area of different land use types were significant and the loss intensities of sediment,organic phosphorus and organic nitrogen transport of each land type increased in the order: forest land<construction land<grassland<farmland. Farmland was the key source area of non-point source pollution loss. If the measures of returning farmland to forests were implemented,the pollution loads of sediment,TN and TP would reduce by 35.8%,46.1% and 35.8%,respectively. Moreover,nitrogen and phosphorus fertilizer applications reduced by 50%,which decreased TN and TP loads by 18.1% and 8.9%,respectively. Therefore,reducing the amount of fertilizer and implementing the measures of returning farmland to forest are the keys to control the non-point source pollution in Siheshui Basin. This study can provide the theoretical basis for watershed ecological environment management.
