Overnight, more than 1.6 million mu of farmland was destroyed in an instant, and more than 230,000 people were unfortunately killed. How did the 758 flood incident in Henan, which caused a sensation in the country, happen? How did the so-called impregnable Banqiao Reservoir collapse?
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In August 1975, a rare rainstorm swept through the Central Plains, eventually triggering the horrific 758 Henan Flood. In this round of natural disasters, a total of 60 dams have collapsed one after another, nearly 10,000 square kilometers have been affected by the disaster, and millions of people have been left homeless overnight. So, how did this catastrophe happen? The story of the flood in Henan, we have to start from the Southern Song Dynasty. We know that in addition to the Yellow River, the Huai River Basin is also the mother river that nurtures the children of China and the cradle of the origin of Chinese civilization. Before the Southern Song Dynasty, the Huai River Basin was relatively stable, and it was also a well-deserved grain producing area for successive dynasties, and the population was extremely dense. However, in 1128, in order to resist the Jin army from going south, the Tokyo general Du Chong changed the course of the Yellow River in Henan Province. Because of this, a large amount of water from the Yellow River was forced to flow into the Huai River from Surabaya, and by 1194, the Huai River ushered in the fourth major diversion.
As a result, the eastern part of Henan, the north of Anhui, and the southwest of Shanxi in the basin have become areas where the Yellow River often floods. It was also from this time that the Yellow River invaded Huaihuai for a long time, and a large amount of silt accumulation made serious changes in the water flooding of the Huai River, and the flooding became more and more frequent, until the last century, the Huai River Basin still had different degrees of flooding every year. So how was the huge flood in Henan caused that year? Do you know what the sensational Banqiao Reservoir dam failure was? After the founding of New China, people began to vigorously control the flooding of the Huai River, of which the Banqiao Reservoir was a benchmark project built in the process of treatment. In 1951, Henan Province gathered four counties and more than 4.2 million people to build the Banqiao Reservoir, which was officially completed after two years. The main body of the Banqiao Reservoir is made of clay ore as raw material, with a height of 24.5 meters, and the total reservoir capacity reaches 490 million cubic meters, of which 375 million cubic meters are built to accumulate floods and the construction target is to resist 300 mm of daily precipitation. It is not difficult to see that it is difficult to encounter floods in a hundred years, and people at that time had great confidence in the flood control ability of the Banqiao Reservoir. However, due to limited technology, the reservoir has gradually cracked since its completion. It was not until 1956 that Soviet engineers reinforced it, and eventually the Banqiao Reservoir was built with only 5 discharges. The original plan was a conservative 12 lanes, and after the restoration was completed, the Soviet side confidently said that this dam was absolutely impregnable. For this reason, the Banqiao Reservoir is also known as the Iron Dam.
It is worth mentioning that at this time, China was in the period of the Great Leap Forward, in order to control the flood, more and more reservoirs were built in the Huai River Basin, which led to a continuous reduction in water flow and more serious pollution. In addition, because the key to building reservoirs at that time was in quantity, not quality, blindly building many reservoirs, resulting in the Huai River being divided by heavy dams. In the decades since, there have been fatal obstructions in the Huai River basin. This also laid one foreshadowing after another for the tragic Banqiao Reservoir collapse in 1975.
In August 1975, Typhoon Lena traveled north along southeast China to northern Henan. It stands to reason that typhoons like Lena disappear soon after reaching the interior. However, the air in the southern hemisphere near Australia erupted northward that year, and the tropical complex in the western Pacific Ocean appeared in North Vietnam, resulting in the typhoon not disappearing after landfall, but instead crossed the Yangtze River with a strong momentum and advanced all the way to the Central Plains. As the warm air in the Pacific Ocean, "Lena" is bound to trigger a series of storms when it meets the cold air in the north. Do you know how tragic the henan floods were forty-six years ago? On August 5, 1975, the storm came unexpectedly, and in the first half of the night, the rainstorm was so heavy that the river overturned the sea, and the daily rainfall at this time had reached 448 mm, which was about 40% more than the local record.
The rainstorm lasted 16 hours and 13 hours, respectively, over the next two days. Within a single consecutive day of the typhoon, Henan's rainfall reached a staggering 1,050 millimeters.
Under the heavy rain, the downstream of the Banqiao Reservoir was hit by floods. To this end, in June, some people proposed to let the Banqiao Reservoir drain the flood, but the application was quickly rejected, citing the fact that the downstream is being affected and the upstream must not be opened. In this way, the Banqiao Reservoir held out for another day, until the No. 7 Banqiao Reservoir decided to discharge the flood. However, the directive was delayed due to the damage to the communication route due to heavy rains. In the early morning of the eighth day, the large reservoir of Shi floodplain announced the collapse of the dam, and the huge amount of 1.2 cubic meters of floodwater accumulated in the reservoir gushed out in more than four hours. At the same time, the capacity of the Banqiao Reservoir has long exceeded the safe water level, and the total reservoir capacity is only 490 million cubic meters of reservoirs, but at this time, it is undertaking nearly 700 million cubic meters of floodwater. At midnight on the eighth day, the flood flooded the dam body, but due to the accumulation of silt, the number of spilled roads was seriously insufficient, and it was impossible to effectively discharge the flood in a short period of time. Under the influence of these unfavorable factors, the huge Banqiao Reservoir also collapsed and the roaring flood after the collapse of two super reservoirs caused a series of chain reactions. 62 dams on the Huai River collapsed one after another. However, the most deadly thing is that after the collapse of the Banqiao Reservoir, a monstrous wave of 10 kilometers wide and 7 meters high was formed. The beast galloped downstream at a speed of 50 kilometers per hour. In the end, this series of tragic dam collapse incidents affected nearly 30 counties and cities, resulting in the instant destruction of more than 1.6 million mu of farmland, more than 10 million people affected, and more than 230,000 people died. Many of them were killed in their sleep. So far, the 758 Henan mega dam collapse incident is still the most destructive reservoir dam failure disaster in history.
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