On the afternoon of October 7, from the high-definition visible satellite cloud image of Fengyun-4, the infiltration of cold air in the central and eastern parts of the mainland and the approach of Typhoon Puppy have formed a large-scale precipitation cloud system, which has shrouded most of the southern part of the mainland in a humid and cool atmosphere of cold air and autumn rain.
1. A 200mm rainstorm hit the vicinity of India
Monitoring data from the Central Meteorological Observatory shows that from yesterday to today, under the influence of typhoon dogs and cold air, a wide range of rainfall areas have appeared in the southern part of the mainland. Among them, the southwest, south China and parts of the eastern part of Jiangnan received heavy rainfall. For example, the outer rain belt of Typhoon Puppy is significantly affecting Guangdong today, and together with the cold air from the south, it has completely extinguished the heat in the Pearl River Delta. Tonight, the temperature at Guangzhou National Station fell below 20 degrees again after nearly 5 months, refreshing a new low in the second half of the year, and the daytime temperature in Shenzhen has always remained below 25 degrees, and the cooling effect is very significant.
More recently, some of the more intense and dangerous rainstorms have occurred in India, next door to the mainland, where a reservoir dam collapsed after a 200-millimetre rainstorm, causing severe flooding. The torrential rainfall flood was the strongest in recent years, and authorities said they had never seen such dangerous torrential rains and floods.
Monitoring data show that since October, the southern foothills of the Himalayas have been experiencing continuous heavy rainfall, and the daily rainfall in the whole state of Sikkim, India on October 4 reached 115~205 mm. Monitoring data from the Central Meteorological Observatory showed that on October 5, the southeastern part of Tibet on the mainland was particularly rainy, and even became the second center of heavy rain besides Typhoon Dog, indicating a large-scale heavy rainstorm on the edge of the Qinghai-Tibet Plateau.
Second, the reservoir dam collapsed
The torrential rains caused the lake to flood and discharge water from South Lonak, directly breaking the dam of the No. 3 hydroelectric power station of the Teesta River downstream. This hydropower station is a large hydropower station that was only put into operation in 2017, and the flood on the 5th directly destroyed the main dam, leaving only a neat section on both sides.
Some netizens have to ask, why is the reservoir dam that was only completed in 2017 so weak and uncontrollable? In fact, Lake Nanlonak, located upstream of the reservoir, is not a simple lake, but a special glacial lake, which has more than quadrupled its water surface area between 1977 and 2008 due to factors such as global warming. Heavy rainfall of about 200 millimeters caused the water level of the glacial lake to rise sharply, and finally collapsed and discharged, directly breaking the dam of the third hydroelectric power station of the Teesta River, triggering a violent flooding in the basin.
Judging from the videos and pictures taken by local netizens, a boulder was stuck in the floodway, and the entire main dam was completely destroyed like cutting tofu, cutting out a very smooth-looking facet.
Floodwaters flowed rapidly down the river, washing away homes, bridges and roads along the river, causing casualties and property damage. It is estimated that at least 18 people have been killed and more than 150 missing as a result of the floods, which have severely affected the lower Teesta river, and caused power and communications to be cut and relief efforts difficult.
Although dams are designed with risk in mind, an unprecedented glacial lake collapse event like this one can easily break these safety thresholds with catastrophic consequences. There are also scholars' satellite data that have conducted detailed satellite studies of the outbreak of Lake Lonak in the south of Sikkim. By comparing satellite imagery at different times, the researchers analyzed the situation before and after the event.
Compared to satellite imagery from October 4, 2023, satellite imagery from September 28, 2023 showed that about 105 hectares of the lake area was drained, which led to a huge amount of lake water leakage, leading to flash floods downstream.
Historically, hydropower projects have been central to addressing energy needs. However, in some countries and regions, insufficient consideration of inherent risks in the construction of hydropower projects will lead to greater risks. Indian authorities have activated a state of emergency, mobilizing the military, police and volunteers to participate in the rescue. Food, water and medical supplies were also provided to the affected areas. At present, rescue efforts are still ongoing. In fact, scientists also pointed out that this event shows that in the context of global warming and climate change, the risk of secondary disasters caused by extreme weather events may exceed expectations.
#Weather##Cold Air##Heavy Rain##Flooding##Typhoon##高温#