Decline of Yangtze River water and sediment discharge: Impact from natural and anthropogenic changes

Abstract

The increasing impact of both climatic change and human activities on global river systems necessitates an increasing need to identify and quantify the various drivers and their impacts on fluvial water and sediment discharge. Here we show that mean Yangtze River water discharge of the first decade after the closing of the Three Gorges Dam (TGD) (2003–2012) was 67 km3/yr (7%) lower than that of the previous 50 years (1950–2002), and 126 km3/yr less compared to the relatively wet period of pre-TGD decade (1993–2002). Most (60–70%) of the decline can be attributed to decreased precipitation, the remainder resulting from construction of reservoirs, improved water-soil conservation and increased water consumption. Mean sediment flux decreased by 71% between 1950–1968 and the post-TGD decade, about half of which occurred prior to the pre-TGD decade. Approximately 30% of the total decline and 65% of the decline since 2003 can be attributed to the TGD, 5% and 14% of these declines to precipitation change, and the remaining to other dams and soil conservation within the drainage basin. These findings highlight the degree to which changes in riverine water and sediment discharge can be related with multiple environmental and anthropogenic factors.

Flow regulation manipulates contemporary seasonal sedimentary dynamics in the reservoir fluctuation zone of the Three Gorges Reservoir, China

“…Monthly water residence times in the mainstream range from 5 to 77 d, with an average value of 27 d, while water replacement in the tributaries is much slower (Xu et al, 2011). Secondly, the dam impounds a water volume that increased from 14 km 3 in 2003 to 24 km 3 in 2006, 37 km 3 in 2008, and 39.3 km 3 in 2010 (Yang et al, 2015). Steps of water impoundment with increasing magnitude and regular water level fluctuation lead to spatial variability in the flooding regime (timing, rate of change, magnitude, frequency, duration) along elevation gradients of this landscape.…”

“…1). It serves a population of 450 million, produces 40% of national GDP, and provides many essential socioeconomic benefits and ecological services to local communities (Yang et al, 2015). Of the more than 5000 dams that have been built across the basin, the Three Gorges Dam is the world's largest hydropower project and the most important water regulation scheme (Fig.…”

“…A large body of literature has quantified the sediment load trapped by the dam, and changes in fluvial sediment export, as well as its hydrological and geomorphological consequences for downstream channels (Yang et al, 2005;Yang et al, 2006;Yang et al, 2007;Chen et al, 2008;Dai et al, 2008;Hu et al, 2009;Xu and Milliman, 2009;Dai et al, 2011;Li et al, 2011b;Wang et al, 2011;Luo et al, 2012;Dai and Liu, 2013;Nakayama and Shankman, 2013;Dai et al, 2014;Feng et al, 2014;Jiang et al, 2014;Lai et al, 2014;Yang et al, 2014;Meng et al, 2015;Yang et al, 2015). A recent study estimated that the annual averaged amount of sediment trapped by the Three Gorges Dam ranged from 116 to 234 Mt/yr during 2003-2012, with an average of 118 Mt/yr (Yang et al, 2014).…”

Erosion patterns in the Changjiang (Yangtze River) catchment revealed by bulk-sample versus single-mineral provenance budgets

“…The Changjiang (Yangtze) River catchment has become in recent years a privileged natural laboratory in which to investigate the relative impacts of climatic, tectonic, and anthropogenic processes on sediment generation and transport (Dai and Lu, 2014;Yang et al, 2015). Diverse methods have been applied to quantify denudation rates, including landscape morphometry, heavy-mineral analyses, bulk-sediment geochemistry, isotope fingerprints of detrital K-feldspar, cosmogenic isotopic tracers, and detrital-zircon geochronology (Chappell et al, 2006;Jie et al, 2007;Yang et al, 2009Yang et al, , 2012Jia et al, 2010b;He et al, 2013aHe et al, , 2014Zhang et al, 2014).…”

Potential Indicator Value of Subfossil Gastropods in Assessing the Ecological Health of the Middle and Lower Reaches of the Yangtze River Floodplain System (China)

“…The vast areas of productive Yangtze River floodplain lakes have been used since the Neolithic Period (7700 cal a BP) for water resource development, including paddy culture, fisheries, irrigation, and navigation [7]. The exploitation for land reclamation, urbanization, and industrialization is at such a magnitude of scales that most lakes have lost their ecological integrity [8,9]. Some lakes have either disappeared, or their areas have been considerably reduced due to reclamation, resulting in unprecedented ecosystem and biodiversity loss in the area, risking the demise of ecological productivity and genetic exchanges of natural populations.…”