During the Shu and Han Dynasties in the Three Kingdoms, Du 'an County was established in Dujiangyan, which was named "Du 'an Weir".
At the same time, it is also called "golden dike", which highlights the water diversion function of fish mouth and uses dike instead of weir as its name.
In the Tang Dynasty, Dujiangyan was renamed "Jueweiyan".
Because the materials and methods of embankment construction at that time were mainly "broken bamboo as a cage, with a diameter of three feet, filled with solid stone, which was called" open tail ".
It was not until the Song Dynasty that Dujiangyan was mentioned for the first time in the history of the Song Dynasty: "Yongkang army ruled Dujiangyan at the age of 20, and the cage stone snake broke the river and stopped water to irrigate several counties."
Regarding the origin of the name Du Jiang, Shu Shui Kao said: "Fu River, a Chengdu River, has two sources, namely Lijiang River and Liujiang River." Liu Jiang is another name for Jian Jiang. On the Chengdu Plain, the Fuhe River is Yongjiang River and the Nanhe River is Jianjiang River. Their upper reaches are Baitiao River and Zouma River, which are divided into Dujiangyan and Neijiang.
"National Records" said: "Du Jiang is the river of Chengdu".
Since the Song Dynasty, the whole Dujiangyan water conservancy project has been generally called Dujiangyan, which accurately represents the whole water conservancy project system and has been used ever since.
Chengdu Plain, known as "Land of Abundance", was a place where floods and droughts were very serious in ancient times.
The lamentation and tragic situation of "until two rulers crowded past in the foggy age of this area" and "man or fish became a turtle" in Li Bai's Shu Dao Nan is a true portrayal of that era.
This situation is caused by the "bad" natural conditions in Minjiang River and Chengdu Plain.
Minjiang River is the main tributary of the upper reaches of the Yangtze River, and the western Sichuan Basin through which it flows is a rainy area in China.
Originated in the southern foot of Minshan Mountain at the junction of Sichuan and Gansu, it is divided into East Source and West Source, the East Source comes from Gonggangling and the West Source comes from Langjialing.
The two sources meet without a dam in Songpan.
It flows southward through Songpan County, Dujiangyan City and Leshan City in Sichuan Province and joins the Yangtze River in Yibin City.
The total length is 793 kilometers, and the drainage area is133,500 square kilometers.
The average slope is 4.83‰, and the annual total water consumption is about 6543.8+0.5 billion m3.
Minjiang River originates from Gonggangling and Langjialing of Minshan Mountain, with a total length of 735 kilometers and a drainage area of 6,543,800 square kilometers. The drop of the whole river is 3560 meters, and the hydraulic resources130,000 kilowatts or more.
Minjiang River is a tributary with the largest amount of water in the upper reaches of the Yangtze River, and Dujiangyan is the upper reaches, mainly for driftwood and hydropower generation. Dujiangyan City to Leshan is the middle reaches, flowing through Chengdu Plain, together with Tuojiang River system and numerous artificial river networks.
Form Dujiangyan irrigation area; Below Leshan is the downstream, mainly shipping.
There are more than 90 tributaries in Minjiang River, with Heishui River and Zagunao River in the upper reaches. Dujiangyan irrigation area in the middle reaches includes Heishi River, Jinma River, Jiang 'an River, Zouma River, Baitiao River and Puyang River. There are Qingyi River, Dadu River, mabian river and Yuexi River downstream.
The main water source comes from the steep right bank of the mountain, and the major tributaries all overflow from the gap of the mountain on the right bank. Rainfall is mainly concentrated in the rainy season, so the water level of Minjiang River fluctuates rapidly and the water potential is turbulent.
The Minjiang River flows southward from the west side of Chengdu Plain to Minshan Mountain Range. For the whole Chengdu Plain, it is an authentic river hanging on the ground, and it hangs badly.
The overall topography of Chengdu Plain is from Minjiang River to Leiyu Mountain, and it is inclined to the southeast with a great slope. Dujiangyan is 50 kilometers away from Chengdu, but the drop is 273 meters. ..
In ancient times, whenever the Minjiang River flooded, the Chengdu Plain was a Wang Yang. Once there is drought, it is thousands of miles away and there is no harvest.
The flood of Minjiang River has long harmed Xichuan, devoured fertile land and infringed on people's livelihood, which has become a major obstacle to the survival and development of ancient Shu.
The establishment of Dujiangyan has its specific historical roots.
During the Warring States Period, people suffering from war longed for the early reunification of China.
Coincidentally, after Shang Yang's political reform, Qin was once famous all over the world, virtuous and virtuous, and the country became stronger and stronger.
They correctly realized the special strategic position of Bashu in the unification of China, and put forward that "if you get Shu, you will get Chu, and if Chu dies, the world will be merged" (Sima Cuo's words).
Under this historical background, at the end of the Warring States Period, Zhao Haoqi of Qin appointed Li Bing, who was familiar with astronomy and geography and lived in seclusion, as the monarch of Shu.
After Li Bing came to power, he first made up his mind to eradicate the flood in Minjiang River, develop agriculture in western Sichuan, benefit the Chengdu Plain and create an economic foundation for Qin to unify China.
Dujiangyan is located where the Minjiang River enters the alluvial plain from the valley, and irrigates thousands of hectares of farmland on the Chengdu Plain east of guanxian.
It turns out that the upper reaches of the Minjiang River flow through steep mountains, and when it reaches the Chengdu Plain, the water speed suddenly slows down, so a lot of sediment and rocks are deposited.
Every year, when the rainy season comes, the water potential of tributaries such as Minjiang River soars and often floods. When there is insufficient rain, it will cause drought. Two or three hundred years before Dujiangyan was built, Du Shu, an ancient Shu state, opened an artificial river at the foot of the Minjiang River to drain the water from the Minjiang River to the Tuojiang River to eliminate water disasters.
In the fifty-first year of Qin Dynasty (256 BC), Li Bing was in charge of Shu County.
On the basis of previous water control, Li Bing built Dujiangyan in guanxian, where the Minjiang River flows into the plain, relying on the local people.
Dujiangyan is a comprehensive water conservancy project for flood control, irrigation and shipping.
Using the middle stream as a weir, Li Bing built a stone ridge in the Minjiang River Gorge, which is called Du Jiang Fish Mouth, also known as Fenshui Fish Mouth.
Yu Zui is a water diversion project, which divides the Minjiang River into two parts.
The one in the east is called Neijiang, which is used to irrigate canals. The west is called Waijiang, which is the main stream of Minjiang River.
On the south bank of Minjiang River near guanxian, there is a separation hill (with the same pile). The detachment mound is a pile of stones separated after rock excavation and sandwiched between the inner and outer rivers.
On the east side of Zilai is the inner estuary, called the bottle mouth, which has the function of controlling water flow.
In summer, the Minjiang River rises, and the fish mouth of Dujiang River is submerged, leaving the water surface and becoming the second water diversion place.
Neijiang enters the dense irrigation system on the western Sichuan plain from below Baokou. Drought will lead to water infiltration, while rainwater will fill the sluice (Huayang State governs Sichuan), ensuring the irrigation of about 3 million mu of fertile land, making Chengdu Plain a capital of drought and flood. The planning, design and construction of Dujiangyan are scientific and creative.
The project planning is quite perfect, and the combination of fish mouth and bottle mouth can distribute flood and low water flow according to the needs of irrigation and flood control.
In order to control the water flow, be a three-stone man at the water inlet and stand in three waters, so that the water is endless and full without shoulders (The Art of Huayang Kingdom).
These stone men obviously play the role of drafts, not manuscripts.
From the determination of the height of the stone man's feet and shoulders, it can be seen that the Minjiang River not only has long-term water level observation, but also has the general law of the variation range of flood and low water level.
By observing the water level of Neijiang water inlet, we can master the inflow, and then adjust the water level with the water diversion project of fish mouth and bottle mouth, so as to control the inflow of the channel.
This shows that as early as 2300 years ago, the working people in our country have mastered and applied the principle that weir flow passes through a certain flow under a certain head. In Dujiangyan, Li Bing made five stone rhinos, two in the depths (the art of Huayang State), and the second in the depths means staying in Neijiang.
The function of stone rhinoceros is different from that of stone man, and its burial depth is used as the control elevation of Shen Tao Beach in Dujiangyan.
Through the deep scouring of the beach, the riverbed can maintain a certain depth and a certain section, so that the riverbed can safely pass through a relatively large flood.
It can be seen that people had a certain understanding and application of the cross-sectional relationship between flow and water at that time.
This quantitative relationship is an important aspect of modern flow formula.