Dai Zhijun.
While most large river-deltas in the world are facing the risk of subsidence and erosion in the Anthropocene, it is suspected that the Changjiang (Yangtze River) Submerged Delta (CSD) could be subjected to the impacts of the world’s largest dam, the Three Gorges Dam (TGD). However, according to the research of Prof. Dai Zhijun of the State Key Lab of Estuarine & Coastal Research and his colleagues, such worry can be eased.
Bathymetric changes and changes in the depocenter location during different periods.
Dai Zhijun, James Liu, Wei Wen and Chen Jiyu found although the TGD may have certain effect on the subsidence and erosion of the CSD, the impact on the estuary submerged delta is not as much as expected. They published their latest findings on Scientific Reports on Oct.16.
A map of China indicating the location of the Changjiang Estuary and the study area.
In their paper, they firstly indicate that the CSD went through high accumulation (1958–1978); slight accumulation (1978–1997), slight erosion (1997–2002); and high accumulation (2002–2009), despite the 70% reduction of the sediment load from upstream since the operation of the TGD in 2003. Meanwhile, at the depocenter of the submerged delta, the accumulation maintained a high rate of 10 cm/yr during 1958–2009. This suggests on a longer term, the distal sediment source from the upstream had little effect on the CSD. Within this time frame the changes in the partition of sediment load among the branching channels of the Changjiang Estuary could likely control the shifting of the depocenter of the CSD on a decadal time scale. Episodic extreme floods and storm surges also increased the magnitude of deposition and erosion of the CSD on short-term scales.
"The impact of the TGD on the environment cannot be shown once for all, so long-term monitoring and dynamic tracking are necessary. And a re-evaluation of the impacts of the TGD on the CSD is urgently needed at present," Dai said.
Written by: Shi Yangyang
Edited by: Liu Jinyu
