The drought in the Yangtze River basin is cyclical. According to the statistics of more than 500 years' historical data from15th century to 20th century, a serious drought event occurred in the Yangtze River basin every 7-8 years on average. The frequency of extreme drought in the middle and lower reaches is higher than that in the upper reaches, about once every 23 to 27 years, and once every 65 years in the upper reaches. From the time of occurrence, the most common drought is summer and autumn, followed by spring drought and summer drought.
This year's drought is mainly caused by the periodic La Nina phenomenon. Since the summer in the northern hemisphere, the atmospheric circulation is abnormal, the Eurasian continent is hot and rainy, and the rainy season in the Yangtze River basin is short. The long-term control of subtropical high in the upper reaches of the Yangtze River in eastern Sichuan, from Chongqing to the middle and lower reaches, is caused by comprehensive factors such as deep typhoons on land and few typhoons.
How much did the water level 15 of the Yangtze River drop on August 20th? Real-time hydrological data show that the Hankou water level in Wuhan section of the Yangtze River 16.74m is 0.0 1m higher than the previous day, and the downward trend of the water level in Wuhan section of the Yangtze River is obviously slowed down.
Real-time hydrological data show that at 7: 00 on August 16, Hankou water level was 17.09 m, and at 7: 00 on August 17, Hankou water level was 16.90 m, which was 0. 19 m lower than the previous day. At 7: 00 on August 18, the water level in Hankou was 16.77, which was 0. 13m lower than the previous day. At 7: 00 on August 20th, Hankou water level 16.73m, down 0.04m from the previous day. In the past three days, the water level in Wuhan section of the Yangtze River has obviously slowed down.
The influence of high temperature and drought on people is affected by high temperature and little rain. At present, the water levels in the main stream of the Yangtze River, Dongting Lake and Poyang Lake are 4.85 to 6. 13m lower than normal, and the water levels in the lower reaches of Shashi River and the two lakes are the lowest in the same period in history. The water surface area of Dongting Lake and Poyang Lake decreased by three quarters compared with that of June. Among them, the water level of Poyang Lake was lower than the low water level on August 4th, setting the record of the earliest low water period since 195 1 was recorded. Sichuan, Chongqing, Hubei, Hunan, Jiangxi and Anhui provinces (cities) have 6.5438+0.232 million mu of cultivated land, 830,000 people have been supplied with water by drought, and 6.5438+0.6 million large livestock have been affected.