From the headwater to the delta: A synthesis of the basin-scale sediment load regime in the Changjiang River

Many large rivers in the world delivers decreasing sediment loads to coastal oceans owing to reductions in
sediment yield and disrupted sediment deliver. Understanding the sediment load regime is a prerequisite of
sediment management and fluvial and deltaic ecosystem restoration. This work examines sediment load changes
across the Changjiang River basin based on a long time series (1950–2017) of sediment load data stretching from
the headwater to the delta. We find that the sediment loads have decreased progressively throughout the basin at
multiple time scales. The sediment loads have decreased by ~96% and ~74% at the outlets of the upper basin
and entire basin, respectively, in 2006–2017 compared to 1950–1985. The hydropower dams in the mainstem
have become a dominant cause of the reduction, although downstream channel erosion causes moderate sediment
load recovery. The basin-scale sediment connectivity has declined as the upper river is progressively
dammed, the middle-lower river is leveed and river-lake interplay weakens. The middle-lower river has changed
from a slight depositional to a severe erosional environment, from a sediment transport conduit to a new sediment
source zone, and from a transport-limited to a supply-limited condition. These low-level sediment loads
will likely persist in the future considering the cumulative dam trapping and depleted channel erosion. As a
result, substantial hydro-morphological changes have occurred that affect the water supply, flood mitigation,
and the aquatic ecosystem. The findings and lessons in this work can shed light on other large river systems
subject to intensified human interference.
Earth-Science Reviews
Leicheng Guo, Ni Su⁎, Ian Townend, Zheng Bing Wang, Chunyan Zhu, Xianye Wang, Yuning Zhang, Qing He