Yangtze sediment decline partly from Three Gorges Dam

Abstract

It could be argued that nowhere has the impact of dams on rivers been more important than in China, where since 1950 almost half of the world's large dams (higher than 15 meters) have been built ]Fuggle and Smith, 2000]. China's Yangtze River (Changjiang)—the largest river in south Asia (1.8 million square kilometers) and whose basin is home to more than 400 million inhabitants—alone has more than 50,000 dams within its watershed, including the world's largest, the Three Gorges Dam (TGD) (Figure 1a ). Water and sediment began being impounded behind the TGD in June 2003, and two years after impoundment, river sediment discharge downstream (at Datong Station) had decreased by nearly half of its 2002 load (Figure 1c). However, the decrease in Yangtze sediment load did not begin with TGD impoundment. Rather, the sediment load at Datong has declined continually since 1987 despite a slight increase in river discharge (Figure 1c ). The change in pre‐TGD loads atYichang, just downstream from the TGD, has been even more extreme, decreasing by approximately 300 million tons in 1986–2002, before declining another 130 million tons after 2002 (Figure 1b). All of this suggests that collective changes on the Yangtze upstream (above Yichang) have been more important in decreasing the river's sediment load than the TGD.

A comparative study of the flux and fate of the Mississippi and Yangtze river sediments

“…1) are the largest rivers in North America and Asia, respectively. Their geological and hydrological conditions and geomorphological evolution have previously been reported for the Mississippi River (Meade et al, 1995;Colman et al, 1998;Roberts, 1998;Day et al, 2007;Bianchi & Allison, 2009;Blum & Roberts, 2009;Horowitz, 2009;Meade & Moody, 2010;Allison et al, 2012) and the Yangtze River (Chen et al, 2001;Yang et al, 2002;Xu et al, 2006;Yang et al, 2006;Xu & Milliman, 2009;Yang et al, 2011). However, only a few papers have directly compared these two rivers (Xu et al, 2007;Bianchi & Allison, 2009).…”

“…3) (Yang et al, 2010). Dam construction, soil-conservation and decline of precipitation in the high-sediment-yield Yangtze upstream have decreased the Yangtze sediment discharge from 480 Mt/year (1953)(1954)(1955)(1956)(1957)(1958)(1959)(1960)(1961)(1962)(1963) to about 150 Mt/year in recent years (Xu et al, 2006;Yang et al, 2011). In contrast to a sharp decline in sediment production in the Mississippi (Fig.…”

The long‐term freshening and nutrient increases in summer surface water in the northern East China Sea in relation to Changjiang discharge variation

“…Xu et al [2006] found that the sediment flux from the Changjiang has decreased since 1950, independently of the long-term Changjiang discharge variation. Previous studies have investigated the long-term variation of nutrient concentration and composition [e.g., Chai et al, 2006;Li et al, 2007], but they mostly covered the region around the Changjiang, its estuary, and its adjacent waters.…”

Long-term changes in nutrient concentrations of the Changjiang River and principal tributaries

“…Over the last several decades, China has experienced rapid increases in chemical fertilizer use and human population (Xing and Zhu 2002;Yan et al 2003). During this same period, thousands of dams have been constructed for the triple functions of energy production (hydrological plants), agricultural irrigation, and flood control (Yang et al 2004;Xu et al 2006). The constructions of the Gezhouba Dam and Three-Gorges Dam on the mainstream of the Changjiang River (Yangtze River) in recent years have caused drastic reductions in sediment fluxes (Xu et al 2006) and a shift in the phytoplankton species in East China Sea (Gong et al 2006).…”