Composition on visiting the ancient weirs of Chengdu and Dujiangyan

During the Spring Festival, our family traveled to Chengdu, the land of abundance. While tasting delicious food, we visited Qingcheng Mountain and Dujiangyan.

We visited the Giant Panda Base, Sanxingdui Ruins, Sichuan Museum and Du Fu Thatched Cottage. During this cultural and food trip, what impressed me most was Dujiangyan, a thousand-year-old weir built on the river.

After listening to the tour guide’s introduction that Dujiangyan is a world-famous ancient water conservancy project, it flashed in my mind that we will see a tall dam today. After entering the scenic spot, based on the tour guide’s explanation, I learned that Dujiangyan was originally It is the earliest dam-less water conservancy project built in 256 BC and still plays a huge role today. Due to flooding in the Minjiang River at that time, crops were not harvested every year. In order to solve the poor life of the people, Li Bing, the governor of Shu County at that time, led his assistants to investigate for three years and formulated a scientific and unique water control plan, and built the Dujiangyan Irrigation Project on the Minjiang River. , mainly composed of three parts: Baopingkou, Yuzui and Feishayan. Only by watching and listening did I understand the excellence of this great project.

At that time, Baopingkou was excavated to divert the floods caused by the Minjiang River blocked by Yulei Mountain, and to divert the river water to the Chengdu Plain on the east coast through Baopingkou. Since gunpowder had not been invented at that time, it was the most difficult to excavate the mouth of the bottle. Li Bing and the craftsmen used the principle of thermal expansion and contraction to first burn the rocks and then pour cold water to make them burst. Because the shape of the mountain pass resembles a bottle The mouth is named "Baopingkou".

Because the terrain of the Minjiang River is high in the east and low in the west, it is difficult to divert the water of the Minjiang River into Baopingkou on the east bank. Li Bing led the craftsmen to use the bend at the mouth of the Minjiang River not far from Yulei Mountain. A diversion weir was built on the original sandbank in the center of the river. The shape resembles the mouth of a fish, so it is called "fish mouth". In order to prevent the weir body from being overturned by the rapid river water, people used the locally abundant bamboos to weave large bamboo cages, put pebbles in them, and then built them into embankments. After the completion of Yuzui, the turbulent Minjiang River was divided into two parts: the outer river and the inner river. The outer river was used for flood discharge, while the water of the inner river flowed to the Chengdu Plain. Yuzui is the main water diversion channel of Dujiangyan. The inner river has a low river bed and a narrow river surface, while the outer river has a high river bed and a wide river surface. In dry and flood seasons, the amount of water flowing into the inner river can be adjusted by adjusting the height of the river bed. The water flowing into the Neijiang River is used for irrigation, and the amount of water used for irrigation needs to be controlled. In order to further divert the flood, Li Bing led people to build a 200-meter-long flying sand at the Yuzui water diversion weir. weir. Feisha Weir has two functions. The first function is to discharge floods. Feisha Weir is about 2 meters higher than the river bed of the Inner River. When the water volume of the Inner River exceeds the upper flow limit of Baopingkou, the excess water will overflow from Feisha Weir; such as In the event of a severe flood, Feishayan will automatically collapse, allowing the water to return to the normal flow of the Minjiang River. The second function is to discharge sand. After the sand discharge effect of the fish mouth, there will still be a certain amount of sand and gravel in the water flowing into the inner river. Feishayan uses the inertial centrifugal force of the curve in front of the weir to throw the sand and gravel from the weir mouth into the outer river. Keep the inner river water flowing smoothly.

Listening to the tour guide’s explanation in simple terms and looking at this great project that embodies the hard work and wisdom of the working people in ancient my country, I was deeply shocked. With it, the Sichuan Plain, which is prone to drought and floods, became the "Land of Abundance"; with it, the talents and strategies of Zhuge Liang and Liu Bei, and the Sichuan poems of Li Bai and Du Fu came into being.