Exacerbating dam-induced fragmentation in China’s river systems
Chenyu Fan, Linghong Ke, Jida Wang, Jim Best, Yunlin Zhang, Yongwei Sheng, Kai Liu, Tan Chen, Fanxuan Zeng, Pengfei Zhan, Jingying Zhu, Jian Cheng, Chunqiao Song
Abstract
Damming-induced fragmentation is arguably the most pronounced anthropogenic disturbance of global river systems, yet its spatio-temporal evolution remains poorly understood due to constraints in dam information, particularly in rapidly developing regions like China. Here we establish a spatially and temporally explicit inventory of Chinese riverine reservoirs and assess the long-term trajectory of damming impacts on river fragmentation during 1970–2020. We find that the number of dams rocketed from 1019 to 17,414, promoting a nearly-fourfold rise in total capacity. Consequently, ~62% of the main rivers, accounting for 90% of the total river discharge in China, have become fragmented. In particular, intensified dam construction in the 1980s and early-21st century substantially altered the free-flowing conditions of main rivers in China, including the Yangtze and Yellow rivers. Over five decades, free-flowing main rivers in China decreased by 38.9%, weakening fluvial ecosystems and threatening long-distance migratory fish species. Notably, our fine-resolution results show that small rivers are fragmented at lengths 3-16 times greater than previously reported, revealing the ongoing river fragmentation spreading to fragile high-altitude headwaters. This underscores the urgent need to consider the societal and eco-environmental effects of such a severely fragmented river system, and aligns with the UN SDGs in promoting sustainable practices. China’s main rivers have experienced a 38.9% decline in free-flowing length and widespread fragmentation, especially in small and high-altitude headwater rivers, due to a surge in dam construction from 1970 to 2020, according to a newly developed high-resolution, spatio-temporal riverine reservoir inventory.