Study of the Three Gorges Dam's Impact on the Discharge of Yangtze River during Flood Season after Its Full Operation in 2009

The impact of the Three Gorges Dam (TGD) on the discharge after its first operation in 2003 has drawn much attention. Most of the existing research focuses on the TGD's impact after its initial operation in 2003. However, the water level first reached the TGD's maximum water level, 175 m, in September 2009. In this paper, to quantify the TGD's impact during flood season after its full operation in 2009, we created a hydrological model to reconstruct the daily discharge unregulated by the TGD from 2003 to 2018 at the five stations downstream from the TGD. The TGD had an impact on the maximum 1-day discharge and maximum 30-day runoff and the coefficient of variation of the daily discharge, but it had less impact on the flood season runoff and the coefficient of skewness of the daily discharge. Additionally, the TGD was only responsible for 18.3% of the change in the maximum 1-day discharge at the Datong station, which is 1123 km downstream from the TGD. Moreover, the TGD had limited impact on the discharge after its initial operation in 2003, but the impact of the TGD on discharge increased after its full operation in 2009. This study helps to show the TGD's impact on the discharge of the Yangtze River from the Yichang station (43 km downstream from the TGD) to the Datong station.