Flood Control Efficiency of Three Gorges Dam

The designed flood control storage of Three Gorges Reservoir is 22.15 billion cubic meters. It could relieve the flood crest by 27000 to 33000 cubic meters per second. The flood control efficiency of Three Gorges Dam tops in the world.

There are a number of people doubting the flood control efficiency of Three Gorges Dam since Chaotianmen Port was submerged during the highest flood crest on July 19. They hold that it is due to the water storage of Three Gorges Dam during the flood season.

Experts explained that the construction of Three Gorges Dam is based on the high mountains and gorges at upper reaches of Yangtze River, then relocated the people under the submerged waterline. Hence there is enough space for the water storage of Three Gorges Reservoir. When the water level of Cuntan reaches 185 meters, the water level of Three Gorges Dam is 150 meters and the backwater of the reservoir even didn't arrived at Fuling. That indicated that the water storage of Three Gorges Reservoir was not responsible to the submerging of Chaotianmen Port.

The middle and lower reaches of Yangtze River is flat and densely populated. It will suffer great losses if Three Gorges Dam is broke by flood. The flood control efficiency of Three Gorges Dam mainly reflected in the protection of the middle and lower reaches of Yangtze River. There is no doubt that the sediment deposit will decrease the storage capacity of Three Gorges Reservoir.

The matter of sediment deposit has been treated as an important matter during the argumentation of Three Gorges Dam. It is also an important matter in the observation during the experimental water storage of Three Gorges Reservoir. Recent years, with the construction of reservoirs, water and soil conservation at upper reaches of Yangtze River, the volume of sediment decreased greatly.

Several foreign experts doubt the real flood storage capacity of Three Gorges Reservoir. The normal storage water level of Three Gorges Dam is designed to be 175 meters. Its flood storage capacity reaches 22.1 billion cubic meters.