Exacerbating dam-induced fragmentation in China’s river systems

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.