Water was discharged from the Three Gorges Dam last weekend to make room for a new deluge from upstream. Photo: Xinhua

People in cities along China’s Yangtze River, which have already been inundated with water, are now scrambling to shore up embankments and dykes before the Three Gorges Dam releases more water and towns are swamped again by the third big flood this summer.

The Yangtze has again become a raging torrent. On Monday evening, stormwater started to pour into the reservoir of the Three Gorges Dam in the Yangtze’s middle reaches at more than 60,000 cubic meters per second.

The amount of water is the same as the peak flow rate 10 days ago, which added more than 10 billion cubic meters of water to the mega-dam’s artificial lake.  

After the National Meteorological Center in Beijing flagged fresh deluge warnings last weekend, the China Three Gorges Group, the dam’s operator, again put itself on a “wartime” footing.

The company lifted the dam’s floodgates and spillways on Saturday and Sunday to discharge water to partially empty the 39.3 billion-cubic-meter reservoir so it could be used to block the expected flood starting from Monday, with tributaries and lakes offstream still overflowing.  

On Tuesday morning, the company said the mass of water flow recorded at the reservoir’s upstream approaches fluctuated between 50,000 to 60,000 cubic meters per second. The plan is to hold as much floodwater as possible to buy time for cities downstream to ramp up their defenses.

Water would be drained into the Yangtze at only 38,000 cubic meters per second to buy some time.

A Xinhua report on Monday quoted the operator as saying the dam’s reservoir already had at least 14 billion cubic meters of additional capacity to slow the flood, and given the current 12,000-cubic-meter-per-second net increase in the flood intake, it would need 13 days to fill the reservoir to the brim.

The theoretical flood regulating capacity of the entire Three Gorges project is 22.15 billion cubic meters. 

The operator of the mega-dam left at least 14 billion cubic meters of capacity in the dam’s reservoir during the past weekend to store the new floodwater, in a bid to mitigate its impact on downstream cities like Wuhan. Photo: Xinhua
Water keeps surging in the Chongqing section of the Yangtze. Photo: Xinhua

In a bid to refute speculation about a possible dam collapse, which was further fueled by a Xinhua report last week admitting a “slight deformation” on some peripheral parts of the structure, Xinhua stressed on Monday that this year’s floods were “severe but not unprecedented.”

“The 61,000-cubic-meter-per-second peak flow recorded on July 19 is thus far this year’s record, but smaller than the 71,200 reading of 2012 when the Three Gorges Dam was put to the toughest test after it was completed in 2002. The mammoth structure on the Yangtze is almost impregnable and all readings of its structural status are well within its design parameters,” said Xinhua. 

The Three Gorges Group also stressed on its WeChat account that the colossal dam was made of 17 million cubic meters of reinforced concrete and as a gravity dam with each section ratcheted to one another, it would withstand the hit of a nuclear bomb as well as floods of “cataclysmic” proportions.

Earlier this month, reports by Taiwanese papers cited Vinayak Bhat, a retired satellite imagery analyst with the Indian Army, as saying the dam could have faced “unexplained pressure” nearing its capacity as it had discharged a large amount of water during June as seen in recent satellite photos, when it was largely dry in the dam’s upper catchment areas.

Multiple videos posted on social media at the end of June also showed Yichang, a prefecture-level city that sits just below the dam, being drenched. Residents there suspected that the flooding could be a result of the dam opening its sluice gates to relieve stress on its structure.

In a retort, the dam’s operator stressed that while focusing on the flood, doomsayers in Taiwan and India should not forget that the dam also housed the world’s largest hydropower plant harnessing the Yangtze. 

“Since when channeling water through a dam to covert the force of water into electricity is regarded as a sign of the dam becoming unstable?” said a post rebutting the reports. 

The western megacity of Chongqing is grappling with a flash flood that usually swamps the city’s embankment along the Yangtze. Photos: Xinhua

Meanwhile, Minister of Water Recourses E Jingping on Monday told an emergency meeting with the Three Gorges Group that a “tight balancing act” must be performed to regulate and mitigate water along the entire Yangtze.

E said other dams and reservoirs in the Yangtze basin, in particular the Dongting and Boyang Lakes that empty into the main river, must stagger their discharge operations to preserve storage capacity to align with the Three Gorges Dam to defend key urban centers including Wuhan, Changsha and Nanchang.   

The National Meteorological Centre has warned of torrential rain continuing to hit the central province of Hubei, where the dam is situated, as well as the upstream provinces of Chongqing, Guizhou and Guangxi and downstream provinces like Hunan, Jiangxi, Anhui and Jiangsu.

These provinces will see 180 millimeters in daily rainfall throughout the rest of the week, with some areas experiencing up to 70mm of rain per hour.

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