Seasonal changes of sediment fluxes in the Yangtze River: roles of precipitation change, human conservation measures in sub-basins, and large dams

Abstract

Abstract Seasonal sediment flux change is a key issue in riverbed evolution and flood control. This paper analyzed variations in sediment fluxes of the Yangtze River in dry and flood seasons during 1961–2014 and the impacts of precipitation change and human interference. Sediment fluxes in both dry and flood seasons decreased by 6.8–74.6 and 14.6–38.7%, respectively, based on daily sediment observations at six mainstream stations. However, precipitation increased sediment yields in both dry and flood seasons by 0.72–4.22 t/km2 (3.5–17.8%) and 4.95–73.32 t/km2 (1.9–25.5%), respectively, based on the reconstructed sediment series without anthropogenic interference. Therefore, sediment reduction due to human conservation measures and dam construction was up to 0.07–20.74 t/km2 (0.9–64.6%) in dry seasons and 27.47–85.35 t/km2 (6.5–23.7%) in flood seasons during 1980–2002, and further reduced 3.61–41.31 t/km2 (46.0–102.9%) in dry seasons and 175.63–471.52 t/km2 (59.6–126.2%) in flood seasons after the Three Gorges Reservoir (TGR) became operational in 2003. Contributions of human activities in six subregions to the reduction of the seaward sediment fluxes were calculated. Therein, the TGR only took up 3.2 and 23.9% in dry and flood seasons, respectively, which is below expectation.