Response of Urban River Water Quality to Spatial Land Use Change in a Riparian Zone Under Different Drainage Systems

[Objective] The objective of this study was to determine how the response relationship between urban riparian land use and water quality changes due to different drainage systems and riparian buffers in order to provide a practical reference for the planning and development of urban riparian zones resulting in improved water environment and ecological restoration. [Methods] We used redundancy analysis and the ecological landscape pattern method with water quality and land use data from Suzhou Creek in Shanghai in 2018 to quantitatively determine the response of river water quality to land use change for different drainage systems and different widths of riparian buffer zones. [Results] ① Land use structure and water quality of the Suzhou Creek riparian area showed obvious spatial and temporal differences between the self-drainage area and the sewer-drainage area. Water quality during the flood season (April-October) was worse than during the non-flood season, and water quality in the self-drainage area was generally better than in the sewer-drainage area. ② Landscape patch density of the water area and agricultural land in the riparian zone of the self-drainage area significantly affected the variation of water quality in the 100—600 m buffer width. ③ Proportion and patch dominance of ecological land significantly affected the variation of water quality in the riparian zone of the sewer-drainage area, and impacted water quality in a range of 100—1 200 meters of the riparian buffer width. ④ Land use accounted for the greatest amount water quality change (56.9%) in the buffer width of the 1 200 m riparian zone in the sewer-drainage area. The explanatory ability of the sewer-drainage area (44.1%—56.9%) was generally higher than that of the self-drainage area (31.1%—52.8%). [Conclusion] There were significant spatial differences in the key variables that influenced the relationship between riparian land use and water quality in the self-drainage area and the sewer-drainage area. In addition, landscape pattern showed a more intensive influence and a larger effect on the variation of water quality in the sewer-drainage area of the riparian zone.