甬江流域土地利用方式对面源磷污染的影响:基于SWAT模型研究

为定量探讨SWAT模型在土地利用方式对面源磷污染影响研究中的适用性,以甬江流域为研究区,构建流域2010年至2014年的SWAT水文水质模型,从水文响应单元的空间尺度上进行了分析研究。结果表明:模型在开展大中流域尺度,长时间序列的土地利用方式对面源磷污染影响的研究中表现良好;流域内林地、建设用地、耕地、园地年均产流深度分别为588.05、729.52、624.26、608.05 mm,产沙年均单位负荷分别为10.09、0.90、44.68、13.29 t·hm-2;总磷年均单位负荷分别为1.42、0.35、9.81、1.82 kg·hm-2。产流深度、产沙单位负荷与总磷单位负荷之间的一元线性回归模型表明:产流、产沙和面源磷之间存在明显的线性关系,且各土地利用方式产沙和磷(R2=0.83～0.88,P0.001)之间的一元线性回归模型预测能力均高于产流和总磷(R2=0.63～0.68,P0.001),表明了面源磷流失的主要载体为泥沙。此外,不同类型土地利用方式下磷输出空间差异性也十分显著,林地在坡度级别为6级时磷流失是2级时的6.90倍;土壤类型RGd(不饱和疏松岩性土)在坡度2级下磷流失是ACu(腐殖质低活性强酸土)的1.15倍,而在6级下是1.42倍。

Impact of land use on non-point sources of phosphorus in the Yong River Basin: SWAT model analysis

This study establishes a SWAT hydrology and water quality model from the year 2010 to 2014 for the Yong River Basin, investigating the impact of land use on the non-point source phosphorus pollution on a hydrological response unit scale. Results showed that the model well-simulated the impact of land-use types of non-point pollution, especially in large basins over long time scales. The average annual runoff depths of forest, urban lands, agricultural lands, and orchards in the Yong River Basin were 588.05, 729.52, 624.26, and 608.05 mm, respectively. The average annual sediment loads were 10.09, 0.90, 44.68, and 13.29 t·hm^-2, respectively. The average annual total phosphorus loads were 1.42, 0.35, 9.81, and 1.82 kg·hm^-2, respectively. The linear regression model showed that there were clear linear relationships among runoff depth, sediment loads, and total phosphorus loads for the different types of land uses. The determination coefficients (R²) of the linear regression model for the sediment load and the total phosphorus load (R²=0.83~0.88, P<0.001) were higher than those for the runoff depth and total phosphorus load (R²=0.63~0.68, P<0.001), indicating that sediment was the main cause for the nonpoint source phosphorus loss. The total phosphorus load demonstrated significant spatial variability under one land-use type. The phosphorus load of the forest at a slope grade of 6 was 6.90 times that at a slope grade of 2. The phosphorus load of RGd soil at slope grades of 2 and 6 were 1.15 and 1.42 times of that of ACu soil, respectively.