The 2008 Wenchuan Earthquake and Intense Post-Earthquake Precipitation: Their Combined Impact on Sedimentation in the Three Gorges Reservoir, China

Abstract

Large earthquakes trigger catastrophic geological hazards, which can impact the runoff and sediment transport not only in affected basins but also in downstream channels. This is particularly true for the Wenchuan Earthquake, which struck on May 12, 2008, in the Longmen Mountain region. In this study, data were collected from representative hydrological stations, and statistical methods along with the Sediment Budget Model were used to investigate the combined impact of the Wenchuan Earthquake and the subsequent intense precipitation on runoff and sediment load changes in rivers affected by it, as well as sedimentation amounts in the Three Gorges Reservoir (TGR). The results revealed an obvious increase in the sediment load at stations along the Fu, Tuo and Min Rivers. Compared to 1999–2007, the annual average sediment load at the stations along the Fu, Tuo and Min Rivers increased by 102.6%–421.9% from 2008 to 2020, except at Gaochang Station. The intense post-Wenchuan Earthquake precipitation events in July 2013, July 2018, and August 2020 led to substantial increases in sedimentation within the TGR, estimated to be approximately 156.9%, 103.8% and 80.1% higher than in normal years. Based on sediment yield data from 2008 to 2020, the removal of earthquake-induced fine-grained sediment is projected to take approximately 33 years. These findings facilitate the understanding of changes in runoff and sediment loads not only in the Upper Yangtze River Basin and the management of the TGR but also in other similar basins.