Reservoirs play a pivotal role in trapping sediments and reducing sediment load into the downstream reach. The construction of reservoirs in the upper Yangtze River had reached its peak since 2003 when the Three Gorges Reservoir was putted into operation. This could greatly change the sediment condition of the Three Gorges Reservoir. To study this effect, this study presented the impact of 66 reservoirs (in operation, under construction, or being planned) in the upper Yangtze River on sediment trapping, based on which sediment load into the Three Gorges Reservoir was predicted. The analysis used the measured 1991-2000 hydrologic series as input, and the calculation of trap efficiency was based on the method proposed by Brune. The results indicate that, due to sediment trapping by the reservoirs, sediment load into the Three Gorges Reservoir drastically reduces to 60 million tons per year, accounting for only 15% of the average yearly sediment load during 1991-2005.
