The Taihu Basin constitutes a complex river network and variable hydrodynamic forces, which contributing to alterations in regional water quality within the Yangtze River Delta. In this study, to explore the underlying mechanism of these dual factors on water quality in the upper Taihu Basin, a combination of graphical analysis, the water quality index (WQI) method, and the partial least square-structural equation model (PLS-SEM) were employed to quantitatively investigate the river structure indices (water surface ratio, W; river system fractal, Δα; river network connectivity, γ) and hydrodynamic force indices (the flow index, FI), and their influence on water quality. Negative correlations were found between both W and Δα with FI and a positive correlation between γ and FI. The southern water network had a higher water body area and greater difference in river network density, while the northern river network had enhanced connectivity and stronger water flow, thus exhibiting superior water quality. Regarding the influence of these factors on water quality, the impact of river structure on WQI was statistically insignificant ( > 0.05), while hydrodynamic force was significantly positively correlated with the WQI ( < 0.05). Moreover, in comparison to the path coefficient of 0.657 for the river structure's influence on the WQI, the hydrodynamic force exerted an even more significant impact on water quality with a path coefficient of 0.715. This study suggested that water quality improvements depend on optimizing the structural integrity of river systems and promoting favorable hydrodynamic conditions, with the latter having greater influence. This research provided theoretical underpinning for optimizing river structure and advancing river and lake water environments within the Taihu Basin.

中文翻译：

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太湖流域上游河流结构和水动力对水质的影响

太湖流域河网复杂，水动力多变，导致长三角区域水质变化。本研究结合图解分析、水质指数（WQI）方法和偏最小二乘结构方程模型（PLS-SEM），探讨太湖上游流域双因素影响水质的潜在机制。采用 ）定量研究河流结构指数（水面比，W；河流水系分形，Δα；河网连通性，γ）和水动力指数（流量指数，FI）及其对水质的影响。 W 和 Δα 与 FI 呈负相关，γ 与 FI 呈正相关。南部水网水体面积较大，河网密度差异较大，而北部河网连通性增强，水流较强，水质优良。从这些因素对水质的影响来看，河流结构对WQI的影响统计上不显着（>0.05），而水动力与WQI呈显着正相关（<0.05）。而且，与河流结构对WQI影响的通径系数0.657相比，水动力对水质的影响更为显着，其通径系数为0.715。本研究表明，水质改善取决于优化河流系统的结构完整性和促进有利的水动力条件，后者的影响更大。该研究为优化太湖流域河流结构、改善河湖水环境提供了理论支撑。