流域"源-汇"景观格局变化及其对磷污染负荷的影响——以天津于桥水库流域为例

基于1999年和2009年天津于桥水库流域两期TM遥感影像,应用遥感解译和空间分析的方法,分析了于桥水库流域"源-汇"景观格局变化特征,通过磷污染过程模型对流域不同景观格局下的磷污染负荷进行空间模拟,并采用情景模拟方法对磷污染空间变化进行了研究。结果表明:(1)10a来,于桥水库流域"汇"型景观格局(林地和灌草地)面积比例减少了18.44%,"源"型景观格局(耕地、园地、村镇及建筑)面积有不同程度的增加,面积比例上升了12.34%。(2)流域不同的"源-汇"景观格局总磷污染负荷模拟值有明显差异。从1999年的1.00(kg/km²)上升至2009年的1.12(kg/km²),上升比例达11％。"源"型景观格局总磷污染量,由1999年的0.98(kg/km²)上升至2009年的1.49(kg/km²),上升幅度达51.5%。(3)3个子流域对磷污染影响存在较大的空间异质性。其中淋河流域总磷负荷最高为1.26(kg/km²),沙河流域总磷负荷为1.14(kg/km²),黎河流域的总磷负荷量最低为1.10(kg/km²)。"源"型景观格局中淋河、沙河和黎河流域中农田景观的总磷量分别为1.93(kg/km²)、1.85(kg/km²)和1.65(kg/km²)。

The source-sink landscape pattern change and its effect on phosphorus pollution in Yuqiao watershed

The relationship between source-sink landscape pattern and phosphorus pollution in Yuqiao watershed(Tianjin) was revealed by use of digital elevation model and phosphorus pollution spatial simulation model on the basis of remote sensing(RS) images interpretation.DEM data at the scale of 1∶50000 were used to extract surface features,identify flow direction,calculate flow accumulation and extract river network in the whole basin using the hydrology module in the ArcGIS spatial analyst tool.Maximum like hood classification algorithm was used to extract land cover information for Yuqiao watershed from the TM images of 1999 and 2009 on which basis landscape change from 1999 to 2009 was statistically analyzed.Spatial distribution of phosphorus pollution in Yuqiao watershed under different landscape patterns were simulated by scenario approach.It is found that the area ratio of sink landscape types of forest,shrub and grass decreased 18.44% whereas that of source landscape types of cultivated land,orchard,built-up increased 12.34%.For the main sub-basins in Yuqiao watershed,namely,Li River,Sha River and Lin River,the area ratio of source landscape types to sink landscape types were 2.81∶1,1.82∶1 and 0.85∶1,respectively in 2009.The total phosphorus pollution of Yuqiao watershed increased significantly from 1.00(kg/km2) up to 1.12(kg/km2) from 1999 to 2009 when the total phosphorus pollution of source landscape has increased 51.5% from 0.98(kg/km2) to 1.49(kg/km2).Significant spatial heterogeneity of phosphorus pollution existed among the three sub-basins with the total phosphorus load in Lin River,Sha River and Li River being 1.26(kg/km2),1.14(kg/km2) and 1.10(kg/km2),respectively.In sum,there were significant temporal and spatial heterogeneity between source-sink landscape pattern and phosphorus pollution in Yuqiao watershed.