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Water projects stand test of strongest floods in 20 years

2020-07-28 Source:China Daily Author:HOU LIQIANG in Beijing and LIU KUN in Wuhan

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The Three Gorges Dam in Yichang, Hubei province, discharges excess floodwater on Monday. The dam has played a key role in flood relief efforts in the middle and lower reaches of the Yangtze River. WANG GANG/FOR CHINA DAILY

Chen Jionghong, who helps divert floodwaters to storage areas in the Yangtze River Basin, has become used to late nights at the office, cold food and instant noodles as the strongest floods in more than two decades hit the region.

Since June, when the Yangtze basin entered its main rainy season, he hardly ever has time to go to the work canteen, even though it's only a five-minute walk from his office in Wuhan, Hubei province.

The canteen staff sends lunch and supper to his office, but the food is often cold by the time he can eat it. For other times, there are instant noodles, said Chen, deputy director of the water conservancy project operation division at the Changjiang Water Resources Commission's Flood and Drought Prevention Bureau.

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Aerial photo taken on July 27, 2020 shows floodwater being discharged from the Three Gorges Dam in Central China's Hubei province. The third flood of the year in the Yangtze River occurred in its upper reaches as the Three Gorges reservoir saw an inflow of 50,000 cubic meters per second at 2 pm Sunday. [Photo/Xinhua]

As the strongest floods since 1998 rage through many areas along Asia's longest river, Chen is just one of thousands of commission employees devoted to flood control.

Based on information from over 30,000 hydrological and rain-monitoring stations, the commission holds joint conferences twice a day. More than 30 of Chen's colleagues take part, including leaders of the commission, a body of the Ministry of Water Resources.

"Based on real time hydrological and rainfall information and forecasts, we discuss the operational plan-which water conservancy projects we are going to mobilize to help store floodwater," he said.

Aside from the conferences, which usually last two to three hours but occasionally run longer, Chen and his colleagues have a lot of other work to grapple with, and treacherous weather can make them even busier.

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Aerial photo taken on July 27, 2020 shows floodwater being discharged from the Three Gorges Dam in Central China's Hubei province. [Photo/Xinhua]

"Some rainfall doesn't fall as forecast. Some downpours may be heavier than predicted. This could result in a flood control situation different from our expectations. In such cases, we have to adjust the operation plans accordingly and in a timely manner," he said.

Once rain falls in the Yangtze basin, the team is informed. Based on water levels and flow rates at hydrological stations and weather forecasts, they determine how to help those downstream avoid inundation.

Over 20 flood control experts regularly work with Chen's department, and they often work late into the night. Amid the complications and difficulties, he often knocks off at around 1 am, but sometimes works until 3 am.

The commission says there are 101 key water conservancy projects facilitating flood control efforts in the Yangtze basin this year, including 41 reservoirs, 46 flood detention areas, 10 pump stations and four water diversion projects.

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Photo taken on July 27, 2020 shows floodwater being discharged from the Three Gorges Dam in Central China's Hubei province. [Photo/Xinhua]

The reservoirs can store 57.4 billion cubic meters of water and the flood detention areas another 59.1 billion cubic meters, it said.

Chen's department also must call all the water conservancy projects involved in the dynamic operational plans and ensure their implementation. "Communication needs to be done repeatedly," he said.

A lot of work has to be done at night. Though his home is only a half-hour drive away, Chen and his colleagues sleep in the office at times to be available when needed. They have to work without a day off during flood season.

"It's not easy for my two children to see me during flood season," he said. "Once they hear the doorbell, they know it's me. They are so excited that they rush to the door."

There are over 52,000 reservoirs in the Yangtze basin, and many discharge water before the rainy season to help accommodate floodwaters.

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Photo taken on July 27, 2020 shows floodwater being discharged from the Three Gorges Dam in Central China's Hubei province. [Photo/Xinhua]

Operation proves effective

The hard work of Chen and his colleagues has paid off. The operation of reservoirs in the upper and middle reaches of the Yangtze have played an important role in avoiding the large-scale evacuation of people near Dongting Lake, the second-largest freshwater lake in China, when the Yangtze was hit by the year's first flood early this month.

Chen Jionghong and Chen Guiya, the commission's deputy chief engineer, rebutted a recent report by Reuters that cast doubt on the effectiveness of the flood mitigation role of the Three Gorges Dam.

Before the Yangtze's first flood of the year arrived at the dam on July 2, the commission drafted a plan to mobilize the Three Gorges reservoir and other major reservoirs in the middle and lower reaches of the Yangtze to help keep the water level at Chenglingji hydrological station below 34.4 meters, which is the maximum design level for dikes in the section.

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Aerial photo taken on July 27, 2020 shows floodwater being discharged from the Three Gorges Dam in Central China's Hubei province. [Photo/Xinhua]

Chenglingji is where the Yangtze meets Dongting Lake.

"The target was met. The highest water level at the station during the time only reached 34.34 meters," Chen Jionghong said, adding that a rough calculation by the commission showed that the water level could have exceeded 35.1 meters without the reservoirs' help.

If the water level at the station had exceeded the maximum level for dikes and kept rising, nearby flood detention areas would have had to be used. That would have necessitated the evacuation of a large number of people from areas to be inundated, he said.

"Our work is people-centered. That is to say, we have to guarantee the safety of people's lives and property," Chen Jionghong said.

Record high water levels at some hydrological stations at Poyang Lake, the country's largest freshwater lake, were cited by Reuters to support the claim that the Three Gorges Dam had failed to play its role in mitigating floods.

But Chen Guiya said that while the Hukou hydrological station, where the Yangtze meets Poyang Lake, is far from the Three Gorges Dam, calculations by the commission showed that the reservoirs in the upper and middle reaches of Yangtze had helped reduce the water level there by 0.2 meters during the first flood of the year.

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Aerial photo taken on July 27, 2020 shows floodwater being discharged from the Three Gorges Dam in Central China's Hubei province. [Photo/Xinhua]

That helped keep the highest water level at the Hukou station to 22.49 meters, 1 centimeter lower than the maximum design level for dike safety and 10 centimeters lower than the record high, even as some stations at the lake hit historic highs. Without the help of those reservoirs, the pressure on flood control around Poyang Lake would have been massive, he said.

"The Three Gorges Dam played a marked role," Chen Guiya said.

He said the help the Three Gorges Dam provided to Poyang Lake was not as notable as that to Dongting Lake because more water entered the mainstream of the Yangtze from its tributaries as the river flowed eastward. Meanwhile, Poyang Lake also got a lot of water from rivers in its own basin. On July 11, for example, over 45,000 cubic meters of water entered the lake each second.

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Aerial photo taken on July 27, 2020 shows floodwater being discharged from the Three Gorges Dam in Central China's Hubei province. [Photo/Xinhua]

Since June, the Yangtze basin has been hit by six episodes of torrential rain with hardly a break. The precipitation in the mainstream of the Yangtze's middle reach and the northern parts of the Poyang Lake basin was more than double the annual average, said Hu Xiangyang, director-general of the commission's Flood and Drought Prevention Bureau.

The rain has gotten heavier this month, with precipitation in the Poyang basin early this month three times the annual average, he said at a news conference on July 20.

The National Meteorological Center said that from June 1 to July 9, the average precipitation in the Yangtze basin reached 369.9 millimeters, the highest in the same period since 1961, and 54.8 mm more than the same period in 1998.

Despite historic precipitation, Chen Jionghong said he is confident the commission is capable of tackling the situation through key reservoirs.

As of July 21, reservoirs in the upper and middle reaches of the Yangtze had helped store 24 billion cubic meters of floodwater, with half of that amount held back by the Three Gorges Dam.

The available floodwater storage capacity of all the key reservoirs stands at about 33 billion cubic meters, Chen Jionghong said.

"We still have capacity large enough to prevent major floods," he said. "The public don't need to worry. We are capable of coping with the situation this year."

Number of key reservoirs to store floodwater during the flood season and their total storage capacity CHINA DAILY


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Editor:Catherine