China Releases Water From Three Gorges Dam To Alleviate Flooding As Torrential Rains Persist

6 Jul 2020 by Staff - Water Diplomat

China's Ministry of Water Resources upgraded its emergency response for flood control from Level Four to Level Three on 4 July, as incessant rains continue across the country. Level One is the highest level of response.

Water levels in the middle and lower reaches of the Yangtze River as well as Dongting Lake and Poyang Lake have been rising as a result of sustained rainfall. A total of 16 rivers in Jiangxi and Anhui were struck by above-warning-level floods, according to the ministry. Coordinated operation of reservoirs in the upper reaches of the Yangtze River will be undertaken to reduce the amount of water flowing into the Three Gorges Dam on the Yangtze, and relieve flood control pressure in the middle and lower reaches of the river.

Authorities at the dam opened three flood discharging outlets 2 July to ease impact of floods on the Yangtze River's lower reaches. Since June 29, the outflow of the Three Gorges Dam has been controlled at an average daily rate of 35,000 cubic meters per second, reducing up to 30 percent of the Yangtze's peak discharge.

The heaviest rains in 70-80 years have caused chaos throughout China’s southwest, with many rivers overflowing and mass evacuations. Disasters have been declared in 24 provinces and municipalities, affecting about 85 million people. The upper reaches of the Yangtze River and the Three Gorges Dam have been especially hard hit. More than 40,000 people have been evacuated and at least 7 children have died in the swiftly moving Fu River, upstream of the dam.

On 20 July water inside the Three Gorges Dam reservoir rose 6 feet above the warning level, and exceeding the flood control line. In Chongqing, over 100,000 tonnes of silt are reported to have been removed to relieve pressure on the reservoir.

Meantime, an internationally-recognised hydrologist has warned of possible the collapse of the Three Gorges Dam, prompting China's government to issue defences about its structural integrity.

The German-Chinese hydologist Wang Weiluo is reported to have said that the Three Gorges Dam’s has serious cracks and that substandard concrete was used in the construction. He has also criticised the design, speed of construction, and quality inspection as all three activities were carried out by the same company.

Wang claims that concrete construction blocks have not been adequately secured to the foundation bedrock. Following a serious 1998 flood, an inspection by independent engineers revealed sub-standard steel bar welding. Google images from 2019 seem to show some bulging or warping of the dam. Wang claims the movement is due to poor design.

At the outset of operations, Chinese state media claimed that the dam was designed to withstand 10,000 year floods; subsequent assessments have stepped-down this claim to 100 years, suggesting a decline in confidence in the dam’s capacity.

Chinese officials defend the condition as “design flexibility” and claim that the apparent deformation is within permissible variation of a few millimetres.

The Government has denied that the dam is at risk. However, Zhao Yunfa, the deputy chief engineer of the overflow dispatch communications center at the Three Gorges Project, has warned: “The flood storage capacity of the Three Gorges is limited. Do not pin your hopes on the Three Gorges Dam.” (Asia Times Financial)

It is estimated that over 400 million people live downstream of the dam, including the cities of Wuhan, Nanjing and Shanghai and any significant overflow or collapse would be disastrous.