Most of the Yangtze River basin is located in southern my country. It has relatively abundant water resources, but this year has been particularly abnormal. According to meteorological forecasts, the drought in the Yangtze River Basin may continue to develop.
Poyang Lake has become a "prairie", and the small fish of Dongting Lake have been dried into dried fish - a few days ago, the news that the " two lakes " entered the dry season 80 days in advance triggered a heated discussion on the Internet. In just two months, the "two lakes" The lake surface has shrunk by three-quarters. Not only that, but the entire middle and lower reaches of the Yangtze River have also experienced a midsummer drought that has not been seen in 60 years.
html On August 17, the Ministry of Water Resources held a press conference on the Yangtze River Basin's drought relief, water supply and autumn grain harvest: Since July, most of the Yangtze River Basin has continued to have high temperatures and little rain, with rainfall 4.50% less than the same period in normal years. ; The inflow of water from the Yangtze River, Dongting Lake, and Poyang Lake systems is 20 to 80% less than the same period in normal years; currently, the water levels in the main stream of the Yangtze River, Dongting Lake, and Poyang Lake are 4.85 to 6.13 meters lower than the same period in normal years, the lowest for the same period since actual measurement records were recorded. The drought in the Yangtze River Basin is developing rapidly. The cultivated land affected by drought in six provinces (cities), Sichuan, Chongqing, Hubei, Hunan, Jiangxi and Anhui, covers an area of 12.32 million acres. 830,000 people and 160,000 large livestock have been affected by the drought and water supply.Changjiang Daily Reporter Comprehensive information released by the Ministry of Water Resources on the 17th: The precipitation in the Yangtze River Basin was the lowest in 60 years; the water in the upper reaches of the Yangtze River was the lowest in 72 years; the water level of Dongting Lake fell below the low water level on August 4, which was the earliest since 1971; Poyang Lake experienced a low water level on August 6, which was the earliest low water level the lake had experienced since 1951.
Luo Jia Chair Professor at Wuhan University and Deputy Director of the Water Resources Professional Committee of the China Hydraulic Society Chen Jin analyzed that historically, summer droughts in the Yangtze River have also occurred, such as this year's situation in 1978 and 2006. The Yangtze River Basin has the highest probability of experiencing consecutive droughts in summer and autumn, with severe drought cycles occurring approximately once every 20 years. What is special this year is that the high temperature weather lasts for a long time, which aggravates the impact of drought. This is a rare situation. The following is a conversation with Chen Jin, a reporter from the Yangtze River Daily -
Climate factors are the main factors affecting the midsummer drought in the Yangtze River Basin
Chen Jin, Luojia Chair Professor of Wuhan University, currently serves as a director of the China Water Resources Strategy Research Association and a water resource major of the China Water Conservancy Society Deputy Chairman of the Committee, Advisory Committee Member of the Hubei Provincial Government, etc.
Reporter: What are the main factors affecting the midsummer drought in the Yangtze River Basin this year? Is it climate change or environmental change?
Chen Jin: The main factor affecting the midsummer drought in the Yangtze River Basin is obviously climate. Drought in the Yangtze River Basin has cyclical characteristics. According to historical statistics from the 15th century to the 20th century, severe drought or above occurs once every 7 to 8 years on average in the Yangtze River Basin. Extreme droughts occur more frequently in the middle and lower reaches than in the upper reaches, about 23 to 27 years. Once a year, compared with about once every 65 years in the upper reaches. In the more than 70 years since the founding of New China, severe drought and extreme drought occurred in 1959, 1978, 2006 and 2011 respectively. In terms of occurrence time, the most common droughts are summer and autumn, followed by spring and summer droughts. The traditional drought and water shortage areas in the Yangtze River Basin are mainly in the Sichuan Basin , central Yunnan region , central Guizhou region , the Hengshao region of Hunan, the southern Gansu region of Jiangxi, the Tangbai River region of the Hanjiang River, and the hilly areas of Hubei and northern Hubei.
The cause of this year's drought is mainly affected by the periodic La Niña phenomenon. Since the beginning of summer in the northern hemisphere of the earth, atmospheric circulation has been abnormal, Eurasia has experienced high temperatures and little rain in a large area, the Yangtze River Basin Meiyu has a short period, and the subtropical high pressure has been controlled for a long time. In the upper reaches of the Yangtze River eastern Sichuan and Chongqing to the middle and lower reaches, combined factors such as fewer typhoons penetrating into the land.
The water level in the Wuhan section of the Yangtze River hit the lowest level in the same period in history since hydrological records were started.Photographed by reporter Xu Weiwei
Reporter: On August 17, the Ministry of Water Resources held a press conference on drought relief and water supply in the Yangtze River Basin to ensure a bumper harvest. At the meeting, it was introduced that "the water levels of the main stream of the Yangtze River, Dongting Lake, and Poyang Lake are 4.85 to 6.13 meters lower than the same period last year. , the lowest in the same period since actual measurement records were recorded." How do you understand this sentence?
Chen Jin: "The water level of the main stream of the Yangtze River, Dongting Lake, and Poyang Lake is 4.85 to 6.13 meters lower than the same period in normal years, the lowest in the same period since actual measurement records were recorded." It can be understood that since the actual measurement data became available, hydrological stations in the Yangtze River and the two lakes areas have been established. Successively, the earliest one was Hankou Station, established in 1865, and other stations were later. The actual measurement data for Dongting Lake and Poyang Lake are estimated to be only 60 to 70 years after the founding of New China. There is also a word "same period" that refers to August 17 in history and does not represent other dates. It may become drier in the future, and if there is heavy rainfall in the later period, the water level may also rise. Therefore, if the same period in history refers to a certain day, the problem is not serious. If it refers to a certain month or the lowest average water level in the entire flood season, the problem is serious.
Tuotuo River is the middle branch of the source of the Yangtze River. means "Red River" in Mongolian. Photographed by special correspondent He Xiaogang
The melting of glaciers will not affect the water coming from the Yangtze River in a short period of time.
Reporter: Just last month, a reporter from the Yangtze River Daily followed the China University of Geosciences (Wuhan) scientific expedition team to visit the source of the Yangtze River. and found that many glaciers had There are signs of accelerated melting, such as Jianggendiru Glacier, Gangjiaquba Glacier , etc. Will the retreat of glaciers have any impact on the water in the upper reaches of the Yangtze River? What are the short-term and long-term effects of glacier melting?
Chen Jin: The issue of is a fact. I have been to the Qinghai-Tibet Plateau and Sanjiangyuan more than 10 times and witnessed the glacier retreat phenomenon. This is a fact global climate warming . However, the water from the Yangtze River source only accounts for 1.4% of the surface water of the Yangtze River. Glaciers melt in a short period of time. It will not affect the flow of water from the Yangtze River within a certain period of time. , but the solid water stored in the source of the Yangtze River (glaciers, permafrost and perennial snow cover) has decreased. In the long run, it will have an impact on my country's climate, hydrology and ecological environment. This is why our country actively participates in global climate negotiations and proposes that our country The reasons for the “double carbon” goal and actively promoting energy conservation, emission reduction, and green development strategies.
Reporter: Will the midsummer dry water in the Yangtze River Basin have any impact on the groundwater in the basin? In particular, is there any threat to drinking water for humans and animals and agricultural irrigation?
Chen Jin: In a short period of time, the low water flow in midsummer in the Yangtze River Basin will not have a significant impact on the groundwater in the basin. Moreover, more than 97% of the water used for human production and living in the Yangtze River Basin is used for surface water in rivers, lakes and water in reservoirs. There is almost no use of groundwater for irrigation in the Yangtze River Basin, and a few rural areas use groundwater. In severe drought areas, drinking water may be difficult for humans and animals. In these areas, on the basis of effective use of large and medium-sized water conservancy projects, five small water conservancy projects such as small water cellars, small pools, small pumping stations, small ponds and small canals can be used. Drill wells, search for mountain springs, and build mobile water pumping facilities to solve water problems in remote areas.
Reporter: In the past, the water levels of Poyang Lake and Dongting Lake dropped significantly in winter, but this year it was in midsummer. Why is this situation happening today? What's the main reason?
Chen Jin: The main reason is that since the beginning of summer, rainfall in the Yangtze River, Poyang Lake, and Dongting Lake basins has decreased significantly compared with normal years. According to statistics from the National Climate Center and the Ministry of Water Resources: from July to August 15, the rainfall in the Yangtze River Basin was 40% less than normal, and the river water was also 20 to 80% less. Not only Poyang Lake and Dongting Lake experienced similar droughts Seasonal water levels and water levels at major hydrological stations on the main stream of the Yangtze River are much lower than normal. The terrain of Poyang Lake is higher than that of the Yangtze River. The water from the five rivers in the Poyang Lake basin (Gan, Fu, Xin, Rao, and Xiu) generally accounts for 85% of the inflow of Poyang Lake. The water from the five rivers has decreased significantly, and the water level of the Yangtze River is also low. , so Poyang Lake entered the dry season ahead of schedule.The water from Dongting Lake includes seven rivers including the Four Rivers (Xiang, Zi, Yuan and Li) and the three mouths of the Yangtze River in Jingnan. The water from these rivers accounts for more than 80% of Dongting Lake. The water from these rivers is relatively small, so Dongting Following Poyang Lake, the lake has also entered the dry season water level.
If there are consecutive droughts in summer, autumn and winter, severe drought may occur
Reporter: There are large-scale water conservancy projects along the Yangtze River, including the Three Gorges Dam and Gezhouba . Why are the regulatory effects limited this year? What are the characteristics of the Yangtze River Basin water cycle ?
Chen Jin: There is a deviation in this issue. Gezhouba does not have the ability to adjust. It is a daily adjustment reservoir and has no ability to replenish water downstream. The Three Gorges Reservoir Although the storage capacity is large, it is a seasonally regulated reservoir. It mainly increases the water volume in the middle and lower reaches of the Yangtze River during the dry season (December to May of the following year). During the flood season (June to September), it is generally at the flood limit water level ( 145 meters), the main purpose is to regulate floods. According to the dispatching rules, the water level of the Three Gorges Reservoir must be lowered to 145 to 146 meters on June 10 every year, and the water level cannot be stored until September to October. Now the Three Gorges Reservoir is around 146 to 147 meters, and there is not much surplus water to increase the amount of water released. The Yangtze River The regulation performance of the large reservoirs in the upper reaches is basically the same. During the flood season, storage capacity is mainly reserved for flood control, and there is not much storage capacity to replenish water to the downstream. However, even so, the reservoir group in the upper reaches of the Yangtze River is still exerting its potential to replenish water to the middle and lower reaches to fight drought.
The water cycle in the Yangtze River Basin is characterized by the synchronization of water and heat. Generally, there are more heavy rains and floods in summer, and less precipitation and runoff in the dry season. During this period, the upstream reservoir groups can continue to increase the discharge flow and replenish water to the downstream. This year is a typical drought year with abnormal climate and short summer rainy season. So far, no typhoons have penetrated into the mainland, so the summer drought phenomenon has occurred.
Reporter: is there currently a better solution for water safety and river protection in the Yangtze River and lakes along it?
Chen Jin: Drought is divided into meteorological drought, hydrological drought, agricultural drought and economic and social drought. Meteorological drought refers to a meteorological phenomenon in which the precipitation in a river basin or region is significantly reduced compared to the average annual average and lasts for a period of time, causing insufficient soil moisture and destroying the moisture balance of terrestrial vegetation. Hydrological drought refers to the phenomenon due to the continuous decrease of rainfall, the decrease of river flow, the decrease of lake or reservoir volume and the decrease of groundwater level. Agricultural drought occurs when precipitation and irrigation systems cannot meet crop growth needs, resulting in reduced crop yields or even no harvests. Economic and social drought refers to a phenomenon in which water levels in rivers, lakes and reservoirs drop or even dry up due to the continued impact of climate and hydrological drought, water intake and water supply guarantee rates of water conservancy projects are damaged, and industrial water use and urban residents have difficulty in using water, resulting in large economic and social losses. Generally, meteorological drought occurs first, then hydrological drought, then agricultural drought, and finally economic and social drought.
At present, the drought in the Yangtze River Basin is still in a state of meteorological drought and hydrological drought. Agricultural drought has occurred in some places. Most rivers and reservoirs still have water. Water conservancy projects such as reservoirs, pumping stations and irrigation play a very important role in drought resistance. Therefore, currently urban areas Residential and industrial water is still guaranteed, as is most farmland irrigation water. If the drought continues to develop, measures such as water demand management such as water conservation and restrictions on water use by high-water-consuming users may be needed. Reporter
: looks at winter from summer. Does this mean that water shortage in the middle and lower reaches of the Yangtze River, including the "two lakes", is a foregone conclusion this winter?
Chen Jin: It is still difficult to say about . If there are typhoons or autumn floods later, the drought will be greatly alleviated, and it will not affect the reservoir water storage after the floods. There will be no problems with water use this winter; if there are consecutive droughts in summer, autumn and winter, severe drought will occur.
(Changjiang Daily reporter Yang Jiafeng)
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