Why did this round of southern floods "break through historical extremes" repeatedly?
Heavy rainfall since June this year has caused floods in many southern provinces. The Central Meteorological Observatory reported on July 7 that from June 1 to July 6 this year, the cumulative rainfall in the Yangtze River Basin was the second most in nearly 60 years, surpassing the 1998 rainfall. At 10 o'clock on July 11th, Jiangxi Province raised the flood control level II emergency response to level I, the water level of Poyang Lake broke through the historical extreme value in 1998, and the flood control situation was extremely severe. At present, the flood control work of Jiangxi Province has entered a wartime state.
As of 12:00 on July 12, this year's flood disaster has caused 37.89 million disasters in 27 provinces (autonomous regions and municipalities) such as Jiangxi, Anhui, Hubei, and Hunan, 141 deaths and disappearances, 2.246 million emergency transfers, 125.8 Ten thousand people needed emergency life assistance; 28,000 houses collapsed; the area of crops affected was 3532 thousand hectares; direct economic loss was 82.23 billion yuan.
Why is there more rain in the southern region this year? How to reduce the losses caused by flood disasters as much as possible? The reporter from the Beijing News talked with four experts to discuss related issues.
Affected by the abnormal ocean temperature in the Indian Ocean, there is more rainfall in the south
Beijing News: In June, the Central Meteorological Observatory issued 31 days of heavy rain warnings, the most in the same period since the warning records were recorded in 2010. Will the 1998 floods in the Yangtze River Basin reappear?
Luo Jingjia: The 1998 Yangtze River flood was affected by the strong El Niño phenomenon. This year is not the same as 1998. Although the warm ocean temperature anomalies also appeared in the Indian Ocean and the Western Pacific, which is conducive to the enhancement of the Western Pacific Subtropical High. The year is somewhat similar, but the tropical sea temperature anomaly is not as strong as in 1998.
The prediction results of the Climate Prediction System of Nanjing University of Information Science and Technology show that in June this year, there was indeed more rainfall in the middle and lower reaches of the Yangtze River, with a strong rainy season. Because the general increase in sea temperature is conducive to the transmission of more water vapor from the ocean to the land, as long as the Western Pacific Subtropical High is strong enough, and the Yangtze River Basin is in a low pressure area, it is easy to produce heavy precipitation in the middle and lower reaches of the Yangtze River.
Beijing News: Affected by rainfall, what is the next direction of the flood disaster in the southern region?
Luo Jingjia: According to our dynamic model, the precipitation in July will be slightly more than in previous years. If this situation continues as it is now, the situation will be more severe. It may improve in August, but precipitation in Central China is still high. Of course, this is only our prediction, and the results are also uncertain.
Beijing News: In stark contrast to the current situation, the southern part of Jiangxi, Anhui, Hubei and other parts of the country suffered from severe drought in the second half of last year. Has this contrast between flood and drought strengthened compared to previous years?
Luo Jingjia: In the summer and autumn of last year, a strong positive dipole phenomenon occurred in the Indian Ocean (editor's note: a strong air-sea coupling phenomenon similar to El Niño but occurring in the Indian Ocean), that is, the East Indian Ocean is very cold, and the West Indian Ocean is a bit Warm, which made the middle and lower reaches of the Yangtze River last year, from the beginning of the rainy season to the autumn, there has been little rainfall, which has caused drought in the region. In terms of the East Asian monsoon, it has a relatively quasi-two-year oscillation phenomenon, corresponding to one year of drought and one year of waterlogging. Last year's drought in the middle and lower reaches of the Yangtze River may be related to this, but the causes that occur each year are not the same. Last year's drought was strongly related to the positive dipole phenomenon in the Indian Ocean.
Cheng Xiaotao: In the 1970s, the impact of drought was greater than that of floods. In the 1990s, the impact of floods exceeded that of droughts. Since the beginning of the 21st century, floods have remained high, and droughts have also risen. Now, floods and droughts are common.
Small and medium-sized rivers become weak areas for flood control, and it is necessary to prevent "little dikes
Beijing News: We often say flood disasters, how to distinguish between flood and waterlogging?
Cheng Xiaotao: Flood and waterlogging, divided into flood and waterlogging disasters. Because the heavy rain gathered in the low-lying places, flooded the community, underground garage, etc. This was a flood. For example, on the first day of the college entrance examination, the Shexian County of Anhui Province was delayed due to severe waterlogging. If it is because of the flooding of rivers that flooded cities and rural areas, this is called flooding. For example, some places in Sichuan and Yunnan have suffered from floods recently.
Furthermore, flood and waterlogging are inseparable. The rise of the river's water level and the formation of floods come from the impact of rainstorms on the one hand, and from the centralized discharge of the drainage system on the other, which is caused by floods. If the water level of the river is too high, the drainage system will be jacked or even reversed, which is caused by flooding. There is a complex interaction between "flood" and "waterlogging".
Therefore, whether it is urban or rural, when it comes to flood control, it cannot be that the housing construction system only considers drainage, and the water conservancy department only considers flood control. The relationship between the two, comprehensively respond to flood disasters.
Beijing News: The Ministry of Water Resources introduced at a recent news briefing that some small and medium-sized rivers have been flooded frequently this year and exceeded historical water levels. Regional storms and floods are heavier than normal. Why have small and medium rivers become weak areas for disaster prevention?
Cheng Xiaotao: China's national defense floods are "levels responsible for level management". The seven major river basins all have river basin management agencies, which are responsible for river basin flood control planning, coordinating the conflicts of interest between upstream and downstream, left and right banks, main tributaries, urban and rural areas, but small and medium-sized rivers do not have special river basin management agencies.
Small and medium-sized rivers often involve multiple administrative regions. In the past, small and medium-sized rivers were under the responsibility of local governments. Which provinces and cities are responsible for small and medium-sized rivers. This has led to many non-systematic flood control projects in small and medium-sized rivers. Moreover, most of the embankments of small and medium-sized rivers are earth embankments, and there is a lack of large controlled reservoirs upstream. Therefore, the pressure of flood control this year is now more reflected in small and medium-sized rivers, which is a high-risk area with frequent floods and recurrences.
In the future, we will start from strengthening defensive inspections, hydrological monitoring and flood forecasting, as well as intensifying the management of small and medium-sized rivers to prevent "small embankments."
Beijing News: Recently, some counties and townships in Sichuan have suffered serious casualties due to floods. Because local counties and towns are built in narrow valleys and live along the river. Does this phenomenon need to change?
Wan Yanhua: Humans are naturally dependent on water. The problem is that there were few people in ancient times, the ecological environmental damage was not as severe as it is now, and the climate change was not as drastic as it is now. There was no problem living there at the time. Now that urbanization is developing too fast, humans demand too much land from lakes and beaches, flood channels are crowded, and floods can easily lead to disasters.
Turn harm into profit, turn flood into resources and use
Beijing News: In the face of flood risk, what is the most important thing?
Luo Jingjia: From the perspective of climate forecasting, we can do a good job in climate forecasting (alarm) by developing regional refined forecasting systems, analyze the probability of possible floods, and give early warnings a few months in advance so that we can Prepare for disaster prevention and mitigation as early as possible.
Zhai Guofang: I think there is another urgent problem to be solved is the problem of consciousness. We must realize that the risk of flooding is one of the many risks we face. In theory, it is impossible to completely eliminate the risk. Therefore, it is necessary to have an understanding of coexistence with risks. The control of flood risk is not only the work of the government, but also the responsibility of each resident. Therefore, the government can't make a big deal, but also has to work with society and residents to jointly prevent floods and waterlogging.
In addition, disaster prevention awareness needs to be further guided and established. Relevant functional departments should develop some related disaster prevention and disaster reduction insurance products, regulate the market behavior of the insurance industry, guide residents to purchase insurance, and play an important role of insurance in disaster prevention and reduction.
Beijing News: How to embed flood control awareness into daily work?
Cheng Xiaotao: The most critical thing is to amend the "Flood Control Law". There is no word "risk" in the "Flood Control Law", which is not conducive to truly doing disaster prevention and mitigation. Therefore, we urgently need to put the risk concept into urban and rural planning management, and we must clarify the flood risk index in different regions. To do a good job in disaster prevention and mitigation, this requires a law. After the establishment of the Emergency Management Department, the entire management system has changed, which is an opportunity.
Wan Yanhua: I think it is necessary to establish a new type of "man-water relationship". Simply defending is not a way to leave enough flood discharge space, not simply building a flood dike once in 30 years or once in 50 years. can. Humans should be good at "fighting floods for profit"-we can build some groundwater reservoirs, and use rainwater or even floods as resources to save and reuse, especially in the northern cities with severe water shortages.
□ Xiao Longping, an interviewer with the Beijing News
Intern Gong Zhengyang
Interview guests
Cheng Xiaotao (Expert of the Expert Committee of the National Disaster Reduction Committee, Former Deputy Chief Engineer of the China Institute of Water Resources and Hydropower Research)
There is no word "risk" in the "Flood Control Law", which is not conducive to truly doing disaster prevention and mitigation. Therefore, we urgently need to put the risk concept into urban and rural planning management, and we must clarify the flood risk index in different regions.
Jingjia Luo (Internationally renowned climatologist, National Distinguished Professor, School of Atmospheric Sciences, Nanjing University of Information Science and Technology)
We can do a good job of climate forecasting (alarm) by developing regional refined forecasting systems, analyze the probability of possible floods, and give early warning months in advance, so that we can prepare for disaster prevention and mitigation earlier.
Wan Yanhua (Professor, School of Architecture and Urban Planning, Huazhong University of Science and Technology)
Mankind must be good at "turning harm into profit". We can build some groundwater reservoirs and use rainwater or even floods as resources for reuse, especially in cities like the North, which are severely water-scarce.
Zhai Guofang (Member of the National "Thirteenth Five-Year Plan" Expert Committee, Director of Nanjing University Urban Security Development Research Center)
Flood risk is one of the many risks we face. In theory, the risk cannot be completely eliminated. Therefore, it is necessary to have an understanding of coexistence with risks. The control of flood risk is not only the work of the government, but also the responsibility of each resident.