Downstream Yangtze River levels impacted by Three Gorges Dam

Abstract

Changes in the Yangtze River level induced by large-scale human water regulation have profound implications on the inundation dynamics of surrounding lakes/wetlands and the integrity of related ecosystems. Using in situ measurements and hydrological simulation, this study reveals an altered Yangtze level regime downstream from the Three Gorges Dam (TGD) to the Yangtze estuary in the East China Sea as a combined result of (i) TGD's flow regulation and (ii) Yangtze channel erosion due to reduced sediment load. During the average annual cycle of TGD's regular flow control in 2009-2012, downstream Yangtze level variations were estimated to have been reduced by 3.9-13.5% at 15 studied gauging stations, manifested as evident level decrease in fall and increase in winter and spring. The impacts on Yangtze levels generally diminished in a longitudinal direction from the TGD to the estuary, with a total time lag of ∼9-12 days. Chronic Yangtze channel erosion since the TGD closure has lowered water levels in relation to flows at most downstream stations, which in turn counteracts the anticipated level increase by nearly or over 50% in winter and spring while reinforcing the anticipated level decrease by over 20% in fall. Continuous downstream channel erosion in the near future may further counteract the benefit of increased Yangtze levels during TGD's water supplement in winter and accelerate the receding of inundation areas/levels of downstream lakes in fall.

The spatial pattern of larval fish assemblages in the lower reach of the Yangtze River: potential influences of river–lake connectivity and tidal intrusion

“…See Table 1 for species codes the Dongting Lake being substantially modified by the Three Gorges Dam, larval fish abundance has greatly declined and the occurrence of larval fish is delayed in this river section . With a much longer distance from the Three Gorges Dam, the influences of the dam on the river section connecting to Poyang Lake are much weaker than Dongting Lake (Wang, et al, 2013). In this regard, the connectivity of Poyang Lake to the Yangtze River provides critical refuge for fishes adapting to the river-floodplain system.…”

Impact of the Three Gorges Dam on the Hydrology and Ecology of the Yangtze River

“…Wang et al [29] reported alterations in the regime of downstream Yangtze levels (Figure 3), resulting from both flow regulation and degradation of the channels due to reductions in the sediment load. Although the TGD releases clear water into the downstream section, the turbulent flows cause large amounts of suspended sediments to be moved downstream, changing the morphological evolution of the river channel.…”

“…Overall, however, continued future erosion of the downstream channel may further act to counteract the benefits ecological obtained by increasing the Yangtze levels (by releasing TGD water) in the winter/fall, and thereby accelerate the decline in the inundation areas/levels of downstream lakes [29]. The shrunken and simplified geomorphology of the Yangtze River, due to the operation of the TGD, has been expected to have direct adverse effects on riparian ecology [13], producing spatially smaller, less diverse riparian ecosystems as compared to the pre-dam period.…”

China’s Policy on Dams at the Crossroads: Removal or Further Construction?

“…The Three Gorges Reservoir (TGR) on the Yangtze River is the largest river regulation and hydroelectric power station in the world [5]. It cost more than US $32 billion to construct and has an operational water level 110 m above the downstream river level.…”