Decadal Sedimentation in China's Largest Freshwater Lake, Poyang Lake

Abstract

Lakes, as key recorders of sedimentation regime variations, have undergone dramatic erosion/deposition worldwide in response to global warming and increasing anthropogenic interference. Poyang Lake, China's largest freshwater lake, has not escaped these variations. Herein, we show that the sedimentation in Poyang Lake has likely undergone a unique phase shift from sediment sink (annually storing 421 × 104 t) during 1960–1999 to sediment source (yearly losing 782 × 104 t) during 2000–2012, with respect to the Changjiang (Yangtze) River. In comparison with sedimentation during 1960–1999, Poyang Lake sedimentation during the period 2000–2012 is characterized by no deposition during the flood season and enhanced erosion during the dry season. Furthermore, Poyang Lake's largest delta, the Ganjiang Delta, prograded at a rate of 32.7 m/a from 1983 to 1996, which increased to 52.8 m/a from 1996 to 2005 but dropped significantly to 1.7 m/a from 2005 to 2015. A sediment core collected in the shallow‐water shoal of the central lake indicates a stable increase in sedimentation flux from 1960 to 2002, with a mean value of 0.27 g/(cm2·a), followed by a decline in sedimentation flux after 2002. Our findings show that the tributary sediment input from the lake catchment dominated the sedimentation of Poyang Lake prior to 2000, when it was significantly larger than the sediment output to the Changjiang River. However, thereafter, the contribution of tributary sediment to the output dropped by 50%, and the rest has been provided by the lake itself. Namely, channels along Poyang Lake's waterway became the additional source of the lake's sediment output in the 2000s.

Large‐scale sedimentary shift induced by a mega‐dam in deltaic flats

“…During the bathymetric surveys, a DGPS device (Trimble Inc.) and a shipborne dual‐frequency echo sounder (ATLAS DESO 17) was used to measure the tidal corrected water depth and site position. The vertical and horizontal errors of measurements are 1.0 and 0.1 m, respectively (Mei et al ., 2018a). All bathymetric datasets were provided by the Changjiang Delta Waterway Administration, Chinese Ministry of Transportation.…”

“…Some sediments were selected and sealed in a plastic box, and placed in a cabinet with a dry and undisturbed environment for at least 20 days to reach equilibrium between 226 Ra and its daughter nuclides. Then, the specific activity of 210 Pb (46.5 keV) and 226 Ra (351.9 keV) were measured using a high‐purity gamma‐ray germanium spectrometer (Canberra Be3830, 777 lead shield; Mirion, Atlanta, GA, USA) (Mei et al ., 2018a). Afterwards, the specific activity of excess 210 Pb ( 210 Pb ex , the difference between the specific activity of 210 Pb and 226 Ra) was calculated.…”

Landward shifts of the maximum accretion zone in the tidal reach of the Changjiang estuary following construction of the Three Gorges Dam

“…Although many previous studies have investigated the morphological response of the Changjiang since the closure of the TGD, these prior works have mainly focused on either the upstream river basin that is completely dominated by fluvial discharge (e.g. Yuan et al, 2012;Lai et al, 2017;Mei et al, 2018;Deng et al, 2019), or the estuarine delta that is directly and significantly affected by tidal asymmetry (Kuang et al, 2013;Luan et al, 2017;. In contrast, much less information is available on the erosion/accretion status of the tidally-influenced reach that links the river basin to the delta, much less to consider how the combined effects of dam construction and altered flow regime have affected the morphology of this critical transition zone.…”

Severely Declining Suspended Sediment Concentration in the Heavily Dammed Changjiang Fluvial System

“…To date, more than 50,000 dams have been built in the river basin, and among them, the largest hydropower project in the world, i.e., the Three Gorges Dam (TGD) is located at the end of the mountain reach of the mainstream, which began to operate in 2003 (S. L. Yang et al., 2011; Z. Yang et al., 2006). The dams have regulated the water flow and altered the transport of sediment and nutrients (Hassan et al., 2010; Zhou et al., 2013, 2015), and the river‐lake relationships are changing (Mei et al., 2018; Yu et al., 2018). The dam‐induced environment and ecosystem disturbances will potentially affect the water security and life quality of the people relying on the river.…”

“…Yang et al, 2006). The dams have regulated the water flow and altered the transport of sediment and nutrients (Hassan et al, 2010;Zhou et al, 2013Zhou et al, , 2015, and the river-lake relationships are changing (Mei et al, 2018;Yu et al, 2018). The dam-induced environment and ecosystem disturbances will potentially affect the water security and life quality of the people relying on the river.…”