Over 3000 large and medium-sized reservoirs have intercepted and stored over 40 billion cubic meters of flood water. Water conservancy projects are preparing for flood control during the flood season

Rainstorm and flood are threatening, and the flood control engineering system is facing challenges.

Since the flood season, rainstorm and flood have occurred in many places in China due to typhoon and heavy rainfall. 484 rivers in 27 provinces, including Heilongjiang, Jilin, Liaoning, Hebei, Beijing, and Shanxi, have experienced floods exceeding the warning level. Among them, 85 rivers have exceeded the protection level, and 39 rivers have experienced the largest floods recorded in actual measurements. At present, the flood process in the Songhua River Basin is still developing, and the flood process in the Haihe River Basin has not yet ended. The operation of the flood storage and detention area is in the most critical period, and the defense situation is still severe.

Large and medium-sized reservoirs comprehensively welcome peak and flood control

On August 4th at 11:00, 96 hours have passed since the first flood of the year occurred on the Yongding River. Downstream of the Lugou Bridge flood diversion hub on the Yongding River in Beijing, the river water is flowing steadily along the main channel of the Yongding River.

Influenced by the No. 5 typhoon "Dussuri", from July 29 to August 2, extreme heavy rainfall occurred in the Haihe River basin, and heavy rainstorm occurred in Beijing, Tianjin, Hebei and other parts of the country. The rain is fierce, and the river water rises sharply. 21 rivers in the five major water systems of the Haihe River Basin, including the North Three Rivers, Yongding River, Daqing River, Ziya River, and Zhangwei South Canal, have experienced floods exceeding the warning level. Among them, the Yongding River Basin has abundant rainfall, strong rainfall, and high flood peaks, with a maximum flood peak of 3750 cubic meters per second at the dam.

How to reduce the momentum of flood peaks, scientifically and finely adjust the main and branch flow reservoirs, and reduce disaster losses is the biggest test for consultation and decision-making.

Minister of Water Resources Li Guoying presided over a special meeting of the Chamber of Commerce, with a video link to the Haihe Water Resources Committee of the Ministry of Water Resources, to study and deploy flood prevention work in the Haihe River Basin.

"The key to flood prevention lies in the scheduling of the basin's flood control engineering system." Li Guoying pointed out that it is necessary to predict the rainfall situation, pre discharge the relevant reservoirs, lower the reservoir water level, calculate the peak flood volume, and accurately and orderly schedule the basin's flood control engineering according to the flood evolution sequence of each water system. The Haihe Water Resources Committee of the Ministry of Water Resources should focus on the key points of scheduling, fully consider the actual situation of upstream and downstream, left and right banks, and main and tributaries, plan collaborative operations, and maximize the potential of reservoir scheduling.

It is understood that there are currently 33 large-scale reservoirs in the mountainous areas of the Haihe River Basin, mostly located at the main river outflows or intersections, controlling over 85% of the mountainous area of the basin. They are an extremely important part of the flood control engineering system.

On July 30th, the Zhaitang Reservoir in Mentougou District, Beijing underwent pre discharge and emptying, but the short-term heavy rainfall on July 31st led to a rapid increase in the reservoir water level. "At one point, the Zhaitang Reservoir exceeded the flood control water level by 11.3 meters. With a maximum inflow of 935 cubic meters per second, the corresponding outflow was only 300 cubic meters per second, with a peak shaving rate of 67.9%." Tao Haijun, director of the Yongding River Management Office of the Beijing Municipal Water Bureau, described the dispatch process as "heart stopping". "The Zhaitang Reservoir has fully realized its designed regulation and storage function, winning time and space for the transfer of more than 4300 people in the downstream Mentougou District.".

Scientific and precise scheduling effectively intercepted floods and significantly reduced losses from flood disasters. Wang Zhangli, deputy director of the Department of Flood and Drought Disaster Prevention of the Ministry of Water Resources, told reporters that as of August 10, 3047 large and medium-sized reservoirs in the Yangtze River, the Yellow River, the Huaihe River, the Haihe River, the the Pearl River, Songliao and the Taihu Lake basins had trapped 41.3 billion cubic meters of flood. Preliminary statistics showed that 806 cities and towns had been flooded, 14571700 mu of farmland had been flooded, and 6.5 million people had been prevented from being transferred.

Reducing Flood Control Pressure in Flood Storage and Detention Areas

Water conservancy engineering is an important safety barrier for flood prevention and control. Among them, water conservancy facilities such as reservoirs, embankments, and waterways are usually regarded as front barriers. However, according to the incoming water situation, when the flood exceeds the capacity of these pre barriers, it is necessary to activate the flood storage and detention area.

The flood storage and detention area refers to the low-lying areas and lakes where floodwater is temporarily stored outside the riverbank, including flood discharge areas, diversion areas, flood storage areas, and detention areas. It is an important component of the main river flood control engineering system and also the bottom card to ensure the safety of flood control in the basin.

In view of the large magnitude of rainstorm floods in Ziya River, Daqing River and Yongding River, the opening of some flood storage and detention areas is inevitable. The Haihe Water Conservancy Commission of the Ministry of Water Resources has closely contacted with Tianjin and Hebei water conservancy departments to conduct joint research and judgment on the use of flood storage and detention areas such as Yongding River flood area and Dongdian Lake, and reported the Request for Instructions on Opening Dongdian Flood Storage and Detention Area to the Ministry of Water Resources 2 days in advance, so as to reserve sufficient time for the transfer and resettlement of personnel in the area in advance.

Wang Zhangli introduced that during the critical period of defending against major floods in the Haihe River Basin, eight national flood storage and detention areas of the four major water systems, including Yongding River, Daqing River, Ziya River, and Zhangwei River, were successively put into use. As of August 8th, 8 flood storage and detention areas have cumulatively diverted 4.049 billion cubic meters of water, with a maximum detention capacity of 2.469 billion cubic meters. The flood control and storage effects are significant, greatly reducing the flood control pressure in Xiong'an New Area and other areas.

On August 7th, all 22 moisture-proof gates of the Duliujian River moisture-proof gate in Tianjin were opened, and floods from the Daqing River and upstream water systems in the Haihe River Basin converged into the Bohai Sea from here. It is understood that the main function of the Duliujian River moisture-proof gate is to divert floodwater from the Haihe River and ensure flood control safety in the Beijing Tianjin Hebei region. Since the launch of the fourth level response by the Haihe River Downstream Bureau on July 28th, the employees of the moisture-proof gate have been on duty 24 hours a day, and they have to operate the moisture-proof gate twice a day during low tide to discharge floods.

Up 67 kilometers from the Duliujian River moisture-proof gate is the Duliujian River flood gate, and further up is the Daqing River. "Approximately 2.5 billion cubic meters of flood in the Haihe River Basin will be discharged from Tianjin this time, mainly from the North Canal, Yongding River floodplain, Dongdian flood storage and detention area, and Baiyangdian. Currently, it has flowed 300 million to 500 million cubic meters." Yang Bang, Deputy Director of the Information Department of the Hydrological Bureau of the Haihe River Conservancy Commission of the Ministry of Water Resources and the first forecaster, said that it is expected that the peak discharge of the Duliu Jianhe River flood gate will reach 1100 cubic meters per second, and the water withdrawal in the Dongdian flood storage and detention area will exceed two months.

Grasp the details and implement various flood prevention measures

At present, China is still in the critical period of "seven bottoms and eight tops" flood prevention. It is expected that in the next week, there will be rainfall processes in the northeast, eastern northwest, and eastern North China. Due to the impact of rainfall, the main and tributaries of Heilongjiang Province, including the Xunbila River and Nenjiang River, will experience a surge in water levels. Among them, the upper reaches of the Wusuli River will experience over warning floods.

Li Guoying stated that the water conservancy system should closely monitor the flood retreat in the Haihe River Basin and the flood evolution process in the Songhua River Basin, and solidly carry out various prevention and response work.

At the same time, for reservoirs operating at high water levels, effective measures should be taken to reduce the reservoir water level during rainfall intervals, to prevent dam collapse, and to ensure downstream safety during large flow discharge. We also need to closely monitor the development and changes of Typhoon No. 6, with a focus on the impact of heavy rainfall on rivers such as the Tumen River, Yalu River, the upper and middle reaches of the Second Songhua River, Mudan River, Lalin River, and Suifen River, and implement flood prevention measures in advance.

At present, the flood process in the Haihe River Basin has not yet ended, and the operation of the flood storage and detention area is in the most critical period. The defense task is still arduous and arduous. The relevant water conservancy departments in the Haihe River Basin should accurately grasp the total amount and process of floods in the Daqing River system, and do a good job in defending key defense objects such as newly built flood diversion embankments, Dongdian flood storage and detention area embankments, and Duliu reduced river embankments, to ensure flood control safety in key areas.

In addition, it is necessary to accurately grasp the distribution of flood retention within the Yongding River floodplain, predict risk points in advance, preset teams, materials, and equipment, and ensure the safety of the embankment in the Yongding River floodplain. On the premise of ensuring the safety of the Duliu Jianhe and Yongding Xinhe embankments, scientific scheduling of the Duliu Jianhe and Yongding Xinhe moisture-proof gates should be carried out, and timely tracing and scouring scheduling should be carried out to reduce sediment accumulation before and after the moisture-proof gates.