It was dug on the long ridge of Minjiang River and extended from Kanshan Mountain (now called Guankou Mountain and Leiyu Mountain). It is a man-made throat to control the flow of water into Neijiang. Because it looks like a bottle mouth and has peculiar functions, it is named Bao bottle mouth. The hill on the right and left of the bottle mouth is named Li dui because it is separated from the mountain. Li Dui was a part of Hutou Rock in Xushan before digging the bottle mouth.
During Du Yu's reign in the ancient Shu kingdom, Prime Minister Ming Kai led the people to dig a wedge-shaped cutting with a bottom width of17m at the gentle slope of Lei Yu on the left bank of Minjiang River. In dry season, the width of the canyon is19m, and in wet season, it is 23m.
Evolution of bottle mouth:
On the right side of the bottle mouth, there was once a rock pillar connected with it, which looked like a trunk, hence the name "trunk". The elephant trunk was washed away by the flood at 1947 due to long-term water erosion and driftwood impact. The rock foundation of Baokou has dried up for a hundred years because of the impact of the rushing river, and a huge suspended cave has appeared.
When Mao Zedong visited Dujiangyan on 1958, he said what would happen after 1000 and 10000! In order to strengthen the rock foundation, in the winter of 1970, the people in the irrigation area blocked the mouth for the first time and drained the deep pool. Starting from the foundations on both sides of the river, more than 8 100 cubic meters of concrete was poured, which built an iron wall for the bottle of Libi and Baokou, making Neijiang, the bottle mouth with automatic water control, more solid and reliable.
Refer to the above content: Baidu Encyclopedia-Treasure Bottle Mouth