基于SWAT模型的农业面源污染尺度效应研究

Scale Effects of Agricultural Non-point Source Pollution Based on SWAT Model

基于SWAT模型建立适用于莲塘口流域的面源污染分布式模型,以子流域嵌套方式从上游至下游构建7个尺度,模拟分析了现状条件及不同情景下总氮、总磷排放负荷随尺度的变化规律。结果表明:随着尺度的增大,单位面积总氮、总磷排放负荷总体呈现逐渐增大的变化规律。原因是稻田是整个研究区域流失氮、磷的主要来源,尺度增大后稻田面积占比增加。当稻田面积比相同时,氮磷排放负荷随尺度的增大而减小,原因是随尺度的增大排水被重复利用以及氮磷被净化使浓度减少。不同水文年型及不同施肥制度下的模拟结果有着相同的尺度变化特征,而且同一尺度上枯水年氮磷排放负荷最少,随施肥量减少氮磷排放负荷减少。

A non-point source pollution distributed model ,which was applied to LianTangkou basin ,was used to simulate and assess the scale effects of nitrogen and phosphorus emission load under current condition and different scenarios ,with 7 nesting scales con‐structed from upstream to downstream .The results showed that the value of pollution emission load per unit area increased along with the nesting scale ,which was attributed to the increased proportion of rice fields＇area .The rice field was the main source of nitrogen and phosphorus emission in the whole research area .However ,the pollution emission load per unit area dropped while the proportion of rice fields＇area remained unchanged among different spatial scales because of the reuse of drainage water and removal of nitrogen and phosphorus pollutants .The simulation results under different level years and different fertilization systems showed the same scale variation as above .At the same time ,the pollution emission load at the dry year was the lowest .Different fertilization systems also showed that the emission load per unit area declined when the farmland fertilizer rate decreased .