TY - JOUR
T1 - Mega-reservoir regulation
T2 - A comparative study on downstream responses of the Yangtze and Yellow rivers
AU - Wu, Xiao
AU - Yue, Yao
AU - Borthwick, Alistair G.L.
AU - Slater, Louise J.
AU - Syvitski, Jaia
AU - Bi, Naishuang
AU - Yang, Zuosheng
AU - Wang, Houjie
N1 - Funding Information:
We extend our sincere gratitude to the Changjiang Water Resources Commission of the Ministry of Water Resources and the Yellow River Conservancy Committee of the Ministry of Water Resources for data support. Additionally, we would like to express our appreciation to Dr. Taian Lu and Mr. Jinhao Guo for their assistance in editing figures. This research was funded by the National Natural Science Foundation of China (No. 42041005 , 42176168 , 42149301 and 52079094 ). Support was also received from the Taishan Scholar Project of Shandong Province (No. TS20190913 and TSQN202211054 ), the Fundamental Research Funds for the Central Universities (No. 202241007 ), the Youth Innovation Team Program in Colleges and Universities of Shandong Province (No. 2022KJ045 ) and Dongying City & College Collaboration Project ( SXHZ-2022-02-15 ). L.S. is supported by UKRI ( MR/V022008/1 ) and NERC ( NE/S015728/1 ).
Publisher Copyright:
© 2023 Elsevier B.V.
PY - 2023/10
Y1 - 2023/10
N2 - Large reservoirs can considerably alter the water-sediment dynamics and morphology of alluvial rivers. Here we review the effects of two mega reservoirs operated with different regulation modes. The Three Gorges Reservoir (TGR) on the Yangtze River has a typical anti-seasonal regulation mode, while the Xiaolangdi Reservoir (XLDR) on the Yellow River undergoes a swift drawdown process shortly before the flood season through the Water and Sediment Regulation Scheme (WSRS). We examine the influence of these regulation schemes on downstream water-sediment dynamics and find that vast sedimentation occurred in both the TGR (128.4 Mt./yr) and XLDR (210.2 Mt./yr). The two rivers have experienced different changes in downstream sediment transport capacity, with coincident flood and sediment peaks in the Yangtze River but with sediment peaks lagging behind flood flow peaks in the Yellow River. On the Yangtze River, highly unsaturated flows from the TGR led to widespread incision downstream, while on the Yellow River, such flows did not induce significant erosion in the first two years following impoundment. The low annual runoff and high sediment yield of the Yellow River mean that riverbed erosion occurred mainly when the water discharge and sediment transport capacity were enhanced by the WSRS. In both rivers, the riverbed eroded and coarsened downstream of the mega dams, lowering the dry season water level. The increase in channel roughness maintained or even raised flood season water levels, potentially increasing flood risk. Sediment budgets reveal that the river segments downstream of the dams switched from sediment sinks to sources due to riverbed incision. Despite new supply from downstream reaches, sediment deficits arising from dam interception and other human activities within the drainage basins have posed significant challenges to the sustainability of the Yangtze and Yellow river deltas, resulting in lower accumulation rates or even transition from progradation to degradation in subaqueous areas. In contrast to the anti-seasonal regulation mode of the TGR, the WSRS of the XLDR has proven very effective at mitigating reservoir sedimentation and has boosted the quantity of sediment reaching the sea, facilitating delta stability and coastal sediment replenishment.
AB - Large reservoirs can considerably alter the water-sediment dynamics and morphology of alluvial rivers. Here we review the effects of two mega reservoirs operated with different regulation modes. The Three Gorges Reservoir (TGR) on the Yangtze River has a typical anti-seasonal regulation mode, while the Xiaolangdi Reservoir (XLDR) on the Yellow River undergoes a swift drawdown process shortly before the flood season through the Water and Sediment Regulation Scheme (WSRS). We examine the influence of these regulation schemes on downstream water-sediment dynamics and find that vast sedimentation occurred in both the TGR (128.4 Mt./yr) and XLDR (210.2 Mt./yr). The two rivers have experienced different changes in downstream sediment transport capacity, with coincident flood and sediment peaks in the Yangtze River but with sediment peaks lagging behind flood flow peaks in the Yellow River. On the Yangtze River, highly unsaturated flows from the TGR led to widespread incision downstream, while on the Yellow River, such flows did not induce significant erosion in the first two years following impoundment. The low annual runoff and high sediment yield of the Yellow River mean that riverbed erosion occurred mainly when the water discharge and sediment transport capacity were enhanced by the WSRS. In both rivers, the riverbed eroded and coarsened downstream of the mega dams, lowering the dry season water level. The increase in channel roughness maintained or even raised flood season water levels, potentially increasing flood risk. Sediment budgets reveal that the river segments downstream of the dams switched from sediment sinks to sources due to riverbed incision. Despite new supply from downstream reaches, sediment deficits arising from dam interception and other human activities within the drainage basins have posed significant challenges to the sustainability of the Yangtze and Yellow river deltas, resulting in lower accumulation rates or even transition from progradation to degradation in subaqueous areas. In contrast to the anti-seasonal regulation mode of the TGR, the WSRS of the XLDR has proven very effective at mitigating reservoir sedimentation and has boosted the quantity of sediment reaching the sea, facilitating delta stability and coastal sediment replenishment.
KW - Channel adjustment
KW - Delta evolution
KW - Reservoir regulation
KW - Reservoir sedimentation
KW - Sediment budget
KW - Water-sediment dynamics
UR - http://www.scopus.com/inward/record.url?scp=85171878261&partnerID=8YFLogxK
U2 - 10.1016/j.earscirev.2023.104567
DO - 10.1016/j.earscirev.2023.104567
M3 - Review article
AN - SCOPUS:85171878261
SN - 0012-8252
VL - 245
JO - Earth-Science Reviews
JF - Earth-Science Reviews
M1 - 104567
ER -