TONG Xiao-xia, WANG Jia-le, PU Jian, ZHANG Wen-jie, HUANG Jin-quan, XU Wen-sheng, WANG Zhi-gang
The relationship between vegetation cover and surface water quality could serve as a technical basis for effective prevention and control of non-point source pollution and improvement of surface water quality. The response of surface water quality to vegetation cover in the city of Shenzhen was investigated indepth by evaluating the surface water quality with the Nemerow’s Pollution Index (NPI) and establishing the relations between surface water quality and vegetation cover and its spatial distribution pattern based on measured surface water quality data and remote sensing image data. Results demonstrate that surface water quality responses notably to vegetation coverage. The NPI, total nitrogen (TN) and total phosphorus (TP) concentrations reduced with the increase of vegetation coverage in the upstream catchment of the study area. Such reduction presented an overall trend from rapid to slow: when vegetation coverage was below 30%, the reduction was rapid, and when vegetation coverage was over 30%, the reduction was slow. The vegetation coverage of 30% can be regarded as a critical point for surface water purification, i.e., when the vegetation coverage reaches 30%, surface water quality will be significantly improved. In addtion, the spatial distribution pattern of land use also has an impact on water quality. When vegetation is distributed in the downstream of catchment area, especially in the waterfront area, the purification effect on surface water would be more significant. According to the research results, we suggested that in urban spatial planning and soil erosion prevention and control of production and construction projects, the green land rate and vegetation coverage should be set at about 30%, and priority should be given to the downstream of the catchment area, especially the area near rivers and reservoirs.
