Dynamic impacts of changes in river structure and connectivity on water quality under urbanization in the Yangtze River Delta plain

• Published in: Ecological indicators 2022-02, Vol.135, p.108582, Article 108582
• Main Authors: Yu, Zhihui, Wang, Qiang, Xu, Youpeng, Lu, Miao, Lin, Zhixin, Gao, Bin
• Format: Article
• Language: English
• Subjects: Relative contribution; River structure and connectivity; The Yangtze River Delta plain; Water quality
• ISSN: 1470-160X; 1872-7034
• DOI: 10.1016/j.ecolind.2022.108582

[Display omitted] •The spatial agglomeration of water quality presents seasonal difference.•The river structure contributes more (more than 60%) to water quality than that of river connectivity.•The river structure indicators have a primary influence (14–18%) on water quality.•The functional connectivity also exerts an influence on water quality. The deterioration of river water quality in urbanized areas is getting more serious, and affects the regional ecology and development of social economy; however, its mechanisms of dynamic variation is still an open question. In this study, we detected the dynamics of water quality and its driven mechanisms in the Yangtze River Delta plain, one of the most developed areas in China. The results showed that the spatial agglomerations of dissolved oxygen (DO), ammonia nitrogen (NH3-N), and total phosphorus (TP) presented seasonal differences, which exhibited a trend of shifting from west to east and then to west from spring to winter. Further, the relative contribution rates of the river network characteristics affecting water quality were quantified on the basis of backpropagation artificial neural networks. We found that the average contribution rates of river structure (more than 60%) were higher than that of river connectivity, and the dominant factors influencing water quality were water surface ratio (WP) and multifractal indices (Δa, Δf). Specifically, the average relative contribution rates of WP, Δa and Δf were 18.72%, 15.03%, and 14.52% during the flood season, respectively, and 15.83%, 16.58%, and 14.54% during the non-flood season. The functional connectivity influenced by obstruction of sluices also influences water quality, which accounting for 11.15% and 12.85% in the flood and non-flood seasons, respectively.