Is the Three Gorges Dam the cause behind the extremely low suspended sediment discharge into the Yangtze (Changjiang) Estuary of 2006?

Abstract

In 2006, the suspended sediment discharge (SSD) into the Yangtze (Changjiang) Estuary, China, reached the historical low value of 85 × 10 6 t. One hypothesis is that this was caused by the second impoundment, i.e. the second stage of the water-level increase behind the Three Gorges Dam (TGD). However, coincidentally, a significant drought occurred in the same year. From our analysis of long-term data on discharge and SSD, we conclude that the SSD decrease in the upstream catchment area resulting from the extreme drought is primarily responsible for the historical low SSD into the Yangtze Estuary. We quantified the contributions of the extreme drought and the second impoundment to the reduction of SSD into the Yangtze Estuary in 2006 as 82% and 18%, respectively. Even though the TGD is the largest dam in the world, the results indicate that the extreme drought conditions had a greater impact than such a manmade river regulation. © 2011 IAHS Press.