AGU: Geophysical Research Letters

 

Editors' Highlight

Sediment retention by China's Three Gorges Dam is causing the Yangtze delta to shrink

China's Three Gorges Dam, which has regulated the waters of the Yangtze River since 2003, is the world's largest dam. Because river damming can damage downstream environments by retaining sediments and nutrients, Yang et al. (2007) sought to quantify how the Three Gorges Dam influences downstream sediment delivery in order to establish sediment budgets in the Yangtze River. They calculated water and sediment supplies from ungauged areas and combined them with data sets from gauging stations, and found that two thirds of the upstream sediment is retained by the Three Gorges Dam each year. The authors also found that in response to this, significant erosion occurs in the riverbed downstream of the dam. However, this erosion does not offset the sediment lost in the reservoir and sediment flux to the Yangtze River mouth has decreased by 31% per year, causing the Yangtze delta to shrink. The authors expect that continued sediment retention at these rates, combined with plans for adding more dams on the watershed, will severely affect the humans and ecosystems that reside on the Yangtze delta.

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