Interview｜Experts from the Academy of Water Sciences: Preliminary prediction that the drought in the Yangtze River Basin will continue and intensify, and the risks are generally controllable

　　The main flood season has not yet ended, but a rare drought has occurred in the Yangtze River Basin.

　　At present, the water levels of the main stream of the Yangtze River and Dongting Lake and Poyang Lake are the lowest since the same period since the actual measurement record, and the small reservoirs in some areas are seriously insufficient.

The Ministry of Water Resources has immediately dispatched the cascade reservoirs in the upper reaches of the Yangtze River with the Three Gorges Reservoir as the core, and the "Four Rivers" reservoirs in Dongting Lake and the "Five Rivers" in Poyang Lake to replenish water downstream, making every effort to ensure the safety of drinking water for the people in the arid areas.

However, it is expected that the drought in the Yangtze River Basin will continue to develop in the next week, and according to the forecast and analysis of the National Climate Center, the possibility of less precipitation in the Yangtze River Basin this autumn is still relatively high, especially in the middle and lower reaches of the Yangtze River.

　　Why does drought occur in the main flood season in the Yangtze River Basin?

What are the lasting effects of the early onset of the drought and the large extent of the drought?

If there is a drought in summer and autumn or even in summer, autumn and winter, what preparations should relevant areas make in advance?

...

　　On August 16, Lv Juan, director of the Flood Control, Drought Relief and Disaster Reduction Center of the China Academy of Water Resources and Hydropower, accepted an exclusive interview with The Paper (www.thepaper.cn). She pointed out that drought disasters in the Yangtze River Basin as a whole showed a trend of frequent and repeated occurrences.

This year's severe drought in the middle and lower reaches of the Yangtze River is similar to the severe drought in Sichuan and Chongqing in 2006. Both are caused by abnormal atmospheric circulation.

　　Lv Juan said that this year's severe drought has the characteristics of early occurrence of drought, long duration, large scale of drought-affected space, and wide-ranging impact of severe drought. Comprehensively considering the weather and underlying surface conditions, combined with the current drought situation, a preliminary diagnosis is made. The drought in the Yangtze River Basin will continue and intensify further.

However, thanks to the important role of water conservancy projects in alleviating drought conditions and ensuring the safety of water for production and domestic use in the region, the risks are generally controllable.

The following is the content of the interview:

Drought covers the upper, middle and lower reaches of the Yangtze River Basin and is relatively rare

The Paper: Why is there a drought in the Yangtze River Basin before the main flood season ends?

Lv Juan:

Since 2000, there have been many summers and droughts in the Yangtze River Basin in China. Typical years are 2006, 2011, 2013 and 2019.

On the whole, drought disasters in the Yangtze River Basin show a trend of frequent and recurring occurrences.

This year's severe drought in the middle and lower reaches of the Yangtze River is somewhat similar to the severe drought in Sichuan and Chongqing in 2006. Both are caused by the abnormal atmospheric circulation and the dry water phenomenon in the main flood season of the Yangtze River Basin.

The Paper: What are the characteristics of this year's drought compared with previous years in terms of the time, scope and extent of the drought?

Lv Juan:

Compared with previous years, this year's severe drought has the characteristics of earlier occurrence of drought, longer duration, larger space affected by drought, and wider impact of severe drought.

　　Since the beginning of June this year, the precipitation in the Yangtze River Basin has started to be less. Among them, it is 20% less in late June and 40% less in July, especially in the mainstream of the lower reaches of the Yangtze River and the Poyang Lake water system, which is 50-70% less than in the past 10 years. The same period is the least.

At present, the water level in the middle and lower reaches of the Yangtze River has continued to decline, which is significantly lower than the same period in history. At 8:00 on August 11, the water level of the main stream in the middle and lower reaches and the exit control stations of the two lakes was 5 to 6 meters lower than the same period of the previous year, ranking among the lowest water levels in August. Top 2 to 4.

　　While the precipitation is seriously low, the temperature in the Yangtze River Basin is seriously high.

Most of the basin have high temperature days for more than 15 days, and some areas in the middle and lower reaches more than 25 days.

　　Affected by low precipitation and high temperature, drought has occurred in 6 provinces (municipalities directly under the Central Government) including Sichuan, Chongqing, Hubei, Hunan, Anhui, and Jiangxi in the Yangtze River Basin since July 2022.

This year's drought has a wide range of occurrences, covering the upper, middle and lower reaches of the main stream of the Yangtze River. It is relatively rare, and it also brings certain difficulties to the emergency dispatch of water in the basin.

Compared with the severe drought in Sichuan and Chongqing in 2006, although the drought has a great impact and severe disasters, the main drought-affected areas are Chongqing and Sichuan provinces (cities) in the upper reaches of the Yangtze River, which are concentrated in the mainstream of the Yangtze River Basin.

　　At present, the drought continues to develop, which has lasted for about 40 days, and may continue to develop in the next week.

As of mid-August, the drought had affected agriculture, drinking water for humans and animals, and ecology.

According to statistics on August 11, the 644.67 thousand hectares of arable land in the above-mentioned 6 provinces (municipalities) were affected by drought, and 830,000 people were affected by the drought.

The drought has had an impact on agricultural production, drinking water for humans and animals, and the ecological environment.

The Paper: What was the longest drought in the Yangtze River Basin?

Lv Juan:

The severe drought in Sichuan and Chongqing in 2006 lasted from mid-May to early September. It started earlier and lasted longer.

The drought lasted for more than 70 days in most parts of Chongqing, including more than 90 days in the northeast and southeast, and more than 100 days in the 6 counties (cities) of Wushan, Wuxi, Fengjie, Wanzhou, Qianjiang and Pengshui.

In Sichuan Province, 21 cities (prefectures) and 139 counties (cities, districts) experienced summer drought successively. The drought lasted for 40 to 60 days in most areas, and the drought in Suining, Nanchong, and Guang'an exceeded 60 days.

The Paper: According to the forecast and analysis of the National Climate Center, there is still a high possibility of less precipitation in the Yangtze River Basin this autumn. If there is a continuous drought in summer and autumn, or even continuous drought in summer, autumn and winter, what kind of lasting impact will it have on relevant areas?

Lv Juan:

As of mid-August, the drought has had a certain impact on agriculture, drinking water for humans and animals, and ecology in the relevant provinces and cities in the Yangtze River Basin.

　　In terms of agricultural production, at present, the first-season rice in Sichuan, Chongqing and other regions in the southwest has begun to fill and become fertile, most of which have entered the milk-ripening stage and mature stage, and some are in the heading and flowering stage, which is the most sensitive period to temperature and water. Severe lack of rain and moisture will lead to a decrease in the seed setting rate, which is not conducive to the formation of the first-season rice yield. The first-season rice in the Jiangnan South China region located in the middle and lower reaches of the Yangtze River is in the stage of jointing to booting, some early-maturing varieties are in the stage of heading and flowering to grain-filling, and double-cropping late rice is in the stage of turning green and tillering. During the period, the impact of high temperature heat damage is obvious.

In addition, continuous high temperature will accelerate the differentiation process of young ears and affect the formation of large ears.

Although the water sources of large and medium-sized irrigation areas can be effectively guaranteed, some Wangtiantian fields and the end of the irrigation areas are severely affected by drought.

　　In terms of drinking water for humans and animals, continuous high temperature and low rainfall have led to the depletion of some scattered water supply projects that use small reservoirs or mountain spring water and stream water as water sources, and some people's water supply has been affected to a certain extent.

As of August 11, 830,000 people in the six provinces (municipalities directly under the Central Government) of Anhui, Jiangxi, Hubei, Hunan, Chongqing and Sichuan in the Yangtze River Basin were affected by drought and water supply.

Among them, Sichuan Province is the most serious, with 342,700 people affected by varying degrees of drinking water, accounting for more than 40% of the total affected population in 6 provinces and cities. A reservoir has dried up, and 476 electromechanical wells have run out of water, affecting 276,000 people and 82,400 large livestock.

　　However, thanks to the construction of water conservancy projects and human-drinking projects in my country in the past ten years, the difficulty of drinking water for humans and animals due to drought has been greatly alleviated.

In 2006, during the peak of the severe drought in Sichuan and Chongqing, one-third of the townships in Chongqing had insufficient water supply, and 8.204 million people and 7.488 million large livestock had difficulty drinking water due to the drought, more than one-fourth of the city's total population. 1.47 million people need water from the government; 4.436 million people and 5.866 million large livestock in Sichuan have difficulty drinking water due to drought, of which 1.35 million people rely on water delivery.

　　In terms of ecological and environmental impact, through the interpretation of remote sensing satellites from 1982 to 2022, from the perspective of terrestrial ecosystems, the degree of impact of drought on ecology from 1982 to 2022 fluctuated and increased, and the upward trend was more obvious after 2010. The degree of impact of drought on the terrestrial ecosystem of the six provinces (cities) from January to July all reached or was close to the maximum value in the same period in history.

Judging from the historical changes in the area of ​​water bodies in the past 20 years, since April 2022, the water body areas of the six provinces (cities) have all reached or approached the lowest level in the same period in history.

Especially since August, with the continued drought in the middle and lower reaches of the Yangtze River, the water levels of Dongting Lake and Poyang Lake have continued to decline, the area of ​​​​grassland and shoal has expanded, large tidal flats have been exposed, and the lake bed has become a vast "prairie", which not only makes aquaculture in the lake area easier , agricultural production has been affected, and the ecosystem of the lake area has been destroyed.

The Paper: Affected by the drought, Dongting Lake and Poyang Lake entered the dry season ahead of schedule. Taking Poyang Lake as an example, the water level at Xingzi Station, its representative station, dropped to 10.35 meters at 8 am on August 16.

What does this mean for the Lake District?

Lv Juan:

Since August, with the continued drought in the middle and lower reaches of the Yangtze River, the water levels of Poyang Lake and Dongting Lake are still declining.

　　Affected by the subtropical high pressure, the Yangtze River Basin is extremely hot, with very little precipitation, while the amount of evaporation is very large, and the inflow of water from the upper reaches of the Yangtze River is relatively low, resulting in a rapid drop in the water level of Poyang Lake, which not only affects the aquaculture and agricultural production in the lake area, but also Destroy the ecosystem of the lake area.

　　First, drinking water is difficult in some areas along the lake.

The dry water in Poyang Lake may cause insufficient water supply at the water intakes of water plants in some counties along the lake, dry ponds in the lakeside villages, drop the groundwater level, insufficient water output from farmers' wells, and difficulties in drinking water.

　　Second, agriculture around the lake may be affected to some extent.

In Jiangxi, September-October is the late rice filling and fruiting period, and agricultural water demand is large. However, with the advance of the dry season, due to factors such as low rainfall and low water level in Poyang Lake, the water supply capacity of existing irrigation facilities has dropped significantly. Water shortages are increasing.

　　Third, the dry water of Poyang Lake will also have a negative impact on the habitat of migratory birds and other ecological and environmental aspects.

It is preliminarily predicted that the drought in the Yangtze River Basin will continue and intensify, but the risks are generally controllable

The Paper: Can the current water conservancy project scheduling be able to meet the needs of production and domestic water in the relevant areas?

Lv Juan:

According to the forecast of the August ensemble forecast product of the European Atmospheric Model from August 13 to August 27, there will be no obvious rainfall process in the Yangtze River Basin in the next two weeks.

According to the national soil moisture forecast, the upper and middle reaches of the Yangtze River, including Sichuan, Chongqing, Yunnan, Guizhou, Hubei and other parts of the region, are in a state of extreme moisture shortage, and the middle and lower reaches are in a state of severe moisture shortage.

Taking into account the meteorology and the underlying surface conditions, combined with the current drought situation, it is preliminarily diagnosed that the drought in the Yangtze River Basin will continue and intensify.

　　In general, although the current large-scale drought in the Yangtze River Basin has caused a certain impact, thanks to the important role of water conservancy projects in alleviating drought conditions and ensuring the safety of water for production and domestic use in the region, the risks are generally controllable.

　　For example, in Hunan Province, water conservancy projects generally prefer to store water compared to previous years. As of August 12, various water conservancy projects stored a total of 37.124 billion cubic meters of water.

Various types of irrigation areas can guarantee the irrigation area of ​​41.32 million mu, the water volume of large and medium-sized irrigation areas can be guaranteed to be irrigated for more than 30 days, and the water volume of small-scale irrigation projects can be guaranteed to be irrigated for more than 15 days; 31,065 rural centralized water supply projects in the province are in normal operation, covering 46.3 million rural people. Drinking water is basically guaranteed.

Yueyang City Huahong Canal Water Supplement Project, Anxiang County Eastern Water Supplement Project, Yiyang City Wuqi Canal Water Supplement Project and other projects have successively opened water diversion projects. The dykes, through the channels in the ridges, transport and transfer water, replenish the lakes and rivers, irrigate fertile fields, and effectively improve the ecological water conditions for local production and living.

The Paper: If the drought continues and intensifies, what preparations should the relevant areas make in advance?

Lv Juan:

This kind of large-scale drought is mainly controlled by the atmospheric circulation of the main climate system. Objectively speaking, it is difficult to predict when it will return to the normal state. Therefore, relevant regions still need to be prepared for prolonged drought.

It is necessary to find out the water shortage situation in drought areas as soon as possible, scientifically dispatch water conservancy projects, implement drought relief plans, ensure the safety of drinking water for the masses, and ensure the drinking water of large livestock and seasonal irrigation water needs of crops.

　　(The Paper Chief Reporter Diao Fanchao)