基于SWAT模型的小流域非点源氮磷迁移规律研究

非点源污染是影响农业水土环境的重要因素。在GIS平台的支持下,运用SWAT模型,以长江下游岔河小流域为研究对象,分析了氮磷流失时空分布规律,并模拟不同灌溉方式下非点源氮磷流失变化。结果表明:率定后的模型适用于小流域非点源污染的模拟;降雨量与径流及有机氮磷流失具有明显的相关关系,汛期(6-9月)的径流量占全年径流量的56.40%,有机氮磷流失量分别占到64.89%和59.70%;在空间尺度上,有机氮与有机磷负荷空间分布相似,呈现出随地表径流向岔河主河道逐渐汇聚的分布特征,大豆和水稻田是非点源污染的主要贡献地区;通过情景模拟发现,不同灌溉方式对小流域氮磷流失影响显著,对水稻田实行优化灌溉,采取浅灌高蓄的控制方法,可以有效改善小流域农业水土环境。

Migration of non-point source nitrogen and phosphorus in small watershed based on SWAT model

Abstract: Non-point source pollution is the main factor affecting water-soil environment. Based on the SWAT model and GIS technology, spatial and temporal distributions of organic nitrogen (ON) and organic phosphorus (OP) were analyzed in Chahe watershed at the lower Yangtze River. Simulation of non-point source pollution was performed under different irrigation methods. The results showed that SWAT model was applicable for the simulation of non-point source pollution in the study area. Precipitation had strong correlation with runoff, ON and OP, with correlation coefficients 0.897, 0.762 and 0.713, respectively. Runoff during flood season accounted for 56.40% of the annual total, while ON and OP accounted for 64.89% and 59.70%, respectively. Loss of ON had a significant correlation with OP loads. At the spatial scale, high loads areas of ON and OP were mainly concentrated in the central and south of the watershed, and as a whole showed a distribution gradually characteristic to the Chahe main channel aggregation with surface runoff. The distribution of ON and OP loads were not only related to the runoff, but also impacted by the land use obviously. Average ON and OP loads of soybean fields were highest at 56.70 and 8.80kg/hm2, respectively, while the total contribution amount of ON and OP in rice fields accounted for 67.87% and 65.72% of the entire watershed, the main contribution of non-point pollution source, respectively. Through scenario simulations, the implementation of optimizing irrigation on rice fields such as shallow irrigation and deep storage, can effectively control nitrogen and phosphorus losses and improve the soil and water environment of small watersheds. This research provides important reference for scientific farmland management of small watershed.