Impacts of Three Gorges Reservoir on the sedimentation regimes in the downstream-linked two largest Chinese freshwater lakes

Abstract

We studied the impacts of Three Gorges Reservoir (TGR) on the sedimentation regimes in the downstream-linked two largest Chinese freshwater lakes, Lake Dongting and Lake Poyang. Our results indicate that up to 1.73 × 109 t sediment was retained in TGR from June 2003 to December 2014. This resulted in a 145.9 × 106 t yr−1 decline in the suspended sediment load at Zhicheng and a 16.8 × 106 t yr−1 lower sediment flow from Yangtze River to Lake Dongting, which partially explains the 13.4 × 106 t yr−1 lower sedimentation in Lake Dongting during the post-TGR period. Furthermore, TGR resulted in a 0.5 ± 0.3 m reduction of the multi-year mean water level at the Lake Poyang outlet Hukou, accelerating the suspended sediment export discharge from the lake. The reduced sedimentation in Lake Poyang during the post-TGR period was estimated to 6.3 × 106 t yr−1. We estimate that a monthly mean concentration of sediment flow from TGR below 0.60 kg m−3 will lead to erosion in Lake Dongting and Lake Poyang. Better regulation of TGR may extend the life expectancy of the two vanishing large lakes.

Anthropocene Geomorphic Change. Climate or Human Activities?

“…However, numerous contributions have pointed out the sediment load reduction experienced by many rivers as a result of human activities (Chang et al, 2019;Dang et al, 2010;Dearing & Jones, 2003;Golosov & Walling, 2019;Gupta et al, 2012;Hu et al, 2009;Hu et al, 2019;Latrubesse et al, 2017;Li et al, 2016;Miao et al, 2011;Rahman et al, 2018;Shi et al, 2017;Vinh et al, 2014;Wang et al, 2011;Wang et al, 2015;Wu et al, 2018;Yang et al, 2002;Yang et al, 2015;Yu et al, 2013;Zhang et al, 2016;Zhou et al, 2016). Reservoir construction, and other modifications of river courses, considerably reduces connectivity between erosion areas in the basins and channel sectors downstream dams, the latter playing a main role (Kondolf, 1997;Graf, 1999Graf, , 2001Graf, , 2005Graf, , 2006Magilligan & Nislow, 2001, 2005Magilligan et al, 2003;Nilsson et al, 2005;Petts, 2009;Dai & Liu, 2013;Magilligan et al, 2013;Petts & Gurnell, 2013;Pal, 2016).…”

How have the river discharges and sediment loads changed in the Changjiang River basin downstream of the Three Gorges Dam?

“…Similarly, the mean water levels at Hukou and Xingzi, a stage station 38 km more inside the Poyang Lake compared to Hukou, have increased between 1960 and 2000 and switched to an afterward decline (Mei et al, 2016;Zhou et al, 2016). It is estimated that one meter water level drop will induce a surface area reduction and water storage volume shrinking by approximately 200-440 million m 2 and 1.3-1.9 billion m 3 , respectively, in the Dongting Lake according to the water level-lake area and water level-storage volume curves (Ding and Li, 2011).…”

Water Identification from High-Resolution Remote Sensing Images Based on Multidimensional Densely Connected Convolutional Neural Networks

“…The disappearance of Poyang Lake is mainly concentrated in the central and southern parts of the lake, leaving only a small part of the water body in the north and northeast. This is principally due to the climatic conditions but is also partly related to the topography, the Yangtze River runoff and the three gorges dam [66,67]. Therefore, for the image of 29 July 2016, these five deep networks have their advantages and disadvantages for the water body identification, but overall show better performances than the NDWI method.…”