10 Years of Three Gorges Project’s 175-m Trial Impoundment: Achievements and Challenges

The Three Gorges Project (TGP) is a backbone project in the development and harnessing of the Yangtze River in China. It has multi-purpose of flood control, power generation, navigation improvement and utilization of water resources. TGP fulfills the yearly impoundment up to its normal pool level of elevation (El.) 175 m, which is of great significance to fully realize its comprehensive benefits. The TGP has been in operation since 2003, following the principle of “impoundment by stages”, its 175-m trial impoundment officially started at the end of the 2008 flood season after completion of the phased impoundment to El. 135 m and El. 156 m. In the past ten years since 175-m trial impoundment, the impoundment operation mode of the TGP has been continuously optimizing by carrying out considerable research and practice of key technologies such as impoundment from the late flood season, and some remarkable results are obtained: the TGP has achieved its 175-m impoundment target for 9 consecutive years since 2010. While giving full play to its comprehensive benefits, the TGP try its best to resolve the contradiction between impoundment and downstream water use in the impounding period. However, climate change, simultaneous impoundment of reservoir group in the upper Yangtze River at the late flood season, and higher requirement on further reducing negative impacts of the TGP’s impoundment on the downstream hydrological regime during the impoundment period have brought new challenges to the TGP’s impoundment operation.