Relating landscape characteristics to non-point source pollution in a typical urbanized watershed in the municipality of Beijing

Landscape characteristics have a substantial effect on non-point source (NPS) pollution. The relationship between landscape characteristics and water quality provides important information for effectively addressing planning and NPS management problems. Multiple stepwise regression analysis and redundancy analysis were integrated to explore the quantitative association between landscape metrics, at both the landscape and class levels, and water quality in the highly urbanized Beiyun River Watershed. The relationship between water quality and the landscape pattern metrics was more significant during the rainy season than after the rainy season. The landscape composition was found to explain 46.9% of the variation in water quality. A total of 60.3% of the variation in water quality could be explained if the landscape configuration metrics were also included in the analysis. This result indicated the importance of the landscape configuration for the water quality of the watershed. Compared with the indices at the landscape level, the class metrics were more effective in predicting water quality. Three metrics, namely, the patch density of water, the largest patch index of forest and the proportion of unused land, could jointly effectively represent the influence of the landscape pattern on the water quality during the rainy season. It is probable that water quality can be improved by maintaining the connectivity of urban rivers, controlling the proportion of unused land and retaining a widespread distribution of unfragmented forest. Furthermore, avoiding the compact distribution of urban land use might reduce the overall emission of pollutants from all forms of transport.