Beijing, China. This study provides robust data support for analyzing dam impacts on river connectivity by constructing a comprehensive database of reservoirs and sluices, alongside a river dataset encompassing five stream orders. Using the Degree of Fragmentation (DOF) and Degree of Regulation (DOR), the research evaluates the 1950–2020 evolution of urban river connectivity and identifies dominant pressure factors for severely impaired reaches. By establishing a high-resolution database, this study significantly enhances the documentation of small-to-medium hydraulic structures and tributaries. Findings indicate that river connectivity impacts have intensified over 70 years, with 17.59% of rivers now severely affected; in some cases, reservoir capacity exceeds average annual runoff. Notably, fine-scale analysis reveals that maximum fragmentation is concentrated in short river reaches, refining the conventional understanding that connectivity increases as river length decreases. This suggests that short urban rivers are more sensitive to dam construction and face higher fragmentation risks. The results underscore the urgent need to address the cumulative ecological effects of small-to-medium dams and prioritize tributary restoration to synergistically advance the national water network. • Development of a comprehensive database of river barriers and rivers. • Incorporating small-to-medium dams, the research was refined. • Assessed the changes in urban connectivity using Beijing as a case study. • The fragmentation of small rivers cannot be neglected.
Li et al. (Thu,) studied this question.
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