GRACE observed mass loss in the middle and lower Yangtze basin

Anthropogenic architectures have a significant impact to the environment. The Three Gorges Dam (TGD), as the largest dam in the world, is a typical example, and has influenced the mass anomalies transported by the flow downstream in the Yangtze River since June 2003. However, the evidence of TGD influence on downstream mass transportation is not documented. In this study, we analyze the monthly gravity solutions from GRACE to investigate the downstream mass variations of Yangtze River. From our results, the considerable mass loss is detected in the downstream of TGD. By comparing our estimations with the in situ water level data of TGD, we find that the mass variations derived from GRACE at Datong station decreases shortly after the impoundment of TGD. This confirms a strong connection between them. Furthermore, by comparing with the in situ sediment load and river discharge at Yichang and Datong gauging stations, we find that the sediment load data shows a similar mass loss signature while the river discharge of both stations has stay at a relative stable level. This indicates that further study is still needed to understand the mechanism better.