Dujiangyan

Dujiangyan is the true hero that led the Minjiang River into the plains and created the 'Land of Abundance' in Sichuan during the 3rd century BC. It was Li Bing, the governor of Shu Prefecture at that time, who led the people to construct the unparalleled Dujiangyan irrigation system. This marvel of engineering scientifically achieved river diversion, flood prevention, and irrigation. Dujiangyan is the first great feat that nurtured the fertile lands of Sichuan. Standing on the open gallery of the tower and looking at the water conservancy project of Dujiangyan from a distance, one can see the Minjiang River rolling down from the mountains. At the turning point, the river is split into two by a long dam shaped like a fish's head. On this side of the dam, the river flows along the foot of Yulei Mountain to a solitary mountain peak, where the embankment is lowered, and the water flow is directed towards the distance along the mountain side. This is the headwork of the Dujiangyan irrigation system. The head of the long dam is called the Fish Mouth, the lowered part at the end of the dam is called the Feisha Weir, and the waterway between the solitary peak and Yulei Mountain is called the Baopingkou. The Fish Mouth, Feisha Weir, and Baopingkou are the three main components of the Dujiangyan project. The Fish Mouth is used for water diversion, allowing irrigation water to enter the inner river and excess water to flow through the outer river; the Feisha Weir is for flood overflow and sediment discharge; the Baopingkou is for channeling water into the canal. The 'Six-Character Mantra' includes deepening the riverbed and lowering the weir for sediment discharge. The Fish Mouth is the main part of the Dujiangyan project, primarily serving the purpose of water diversion. The dam, shaped like a fish's mouth, divides the Minjiang River into two streams: the inner river and the outer river. Due to the riverbed being higher on the outside and lower on the inside, coupled with a bend in the river, when the water flow is low during the spring plowing season, about 60% of the mainstream enters the inner river, ensuring irrigation water for the Chengdu Plain. During the flood season, when the flow increases sharply and the water level rises significantly, the water momentum is noticeably reduced due to the bend in the riverbed. Since the outer river has a wider channel than the inner river, the flow into the inner river automatically becomes less than that of the outer river, with about 40% of the water entering. This greatly solves the flood prevention problem for the Chengdu Plain. This function is what is referred to in the 'Three-Character Classic' of Dujiangyan as 'dividing four and six, leveling floods and droughts.' The Fish Mouth also has a certain function of sediment and stone discharge. The Minjiang River is one of the largest tributaries of the Yangtze River, originating from Songpan County within our province, and is considered part of the middle and upper reaches.