Spatial and temporal sedimentation changes in the Three Gorges Reservoir of China

Abstract

This study examined the temporal trend of sedimentation in China's Three Gorges Reservoir (TGR) from compiled sediment data at multiple temporal scales. Based on decade-averaged annual sediment loads, a decreasing trend of sediment supply between 1950s and 2000s was found, with a lower-than-expected mean sedimentation rate. From 2003 to 2013, the annual sediment supply generally decreased, with the annual sediment deposition rate being about 50% less than that predicted with prior numerical models. The reduced annual sedimentation rate was attributed to (relatively) small dam building within the upstream watershed, conservation activities and sand/gravel mining. Morphological changes at two cross sections within the TGR between 2003 and 2013 indicated that sediment deposition caused only limited bed accretion along the main course of the TGR. In the tail area of the TGR, where sediment transport ceases first, the sedimentation occurring between 2004 and 2013 was insufficient to impede navigation. These results indicate that at least as a first approximation sedimentation in the TGR is well controlled, making it a subdued 'river dragon'.

Measurements of the sediment flocculation characteristics in the Three Gorges Reservoir, Yangtze River

“…In the demonstration phase of the TGR, many studies have simulated and predicted that sediment finer than 0.01 mm will be suspended as wash load and will not deposit in the TGR (Lin & Zhang, 1989; Science and Technol- , 2002). However, in the post-TGD period, research has indicated the following: that the particle diameter of the sedimentation is between 0.001 and 0.25 mm, a sediment finer than 0.008 and 0.016 mm contributes to 44 and 61% of total sedimentation, respectively, and that flocculation occurs in the TGR (Li et al, 2011(Li et al, , 2018Gao et al, 2015).…”

“…It was concluded during the demonstration phase that sediments finer than 0.01 mm were wash load with no deposition in the TGR (Lin & Zhang, 1989). However, the actual sedimentation was mainly distributed in the wide reaches of the permanent backwater region in the TGR, and approximately half of the total sedimentation in the TGR was fine particles with diameters less than 0.01 mm (Gao, Wang, & Siegel, 2015;Li et al, 2018;Yang et al, 2014). Tsai, Iacobellis, and Lick (1987) and Williams, Walling, and Leeks (2007) found that the fine sediments in rivers and lakes could be flocculated, and many studies have also confirmed the flocculation of fine sediments in the TGR by various means such as onsite measurement, numerical simulation, and experimental research.…”