Dujiangyan (都江堰)
During the dry season in winter and spring, when the flow of water from the mountains is low, using the Waijiang Floodgate (外江闸), the levee segregates 60% of the river’s flow into the Inner Stream (内江) meant for irrigating the Chengdu Plain (成都平原). In summer and in times of heavy rainfall, only 40% is diverted inward with the other 60% cast out into the Outer Stream (外江) to prevent the lowlands from flooding.
The Waijiang Floodgate controls the flow of water to the Outer Stream...
The Flying Sand Weir (飞沙堰) has a 200 m-wide opening that connects the inner and outer streams. This further safeguards against flooding by allowing the natural swirling flow of the water to drain out the excess water from the inner to the outer stream. The swirl created also sieves out the silt and sentiment to prevent it clogging the inner stream. This debris is then excreted into the outer stream. A modern reinforced concrete weir has replaced Li Bing’s original weighted bamboo baskets.
Merlion Wayfarer finds this portion the most ingenious, as the inventor actually thought of expelling the debris and sediment back to the fastflowing river using a system of rocks to filter these out...
The other components of Dujiangyan as viewed from Qinyan Tower...
A distant pagoda in the Outer Stream...
Sichuan (四川), China (中国)
April 2013
Components of Dujiangyan's Irrigation System
Dujiangyan consisted of several key components:
Fish Mouth Levee (鱼嘴)
The Fish Mouth Levee (鱼嘴), named for its conical head that is said to resemble the mouth of a fish, is the key part of Li Bing’s construction. Through a spread of smaller "islands" made of rocks before it, this artificial levee divides the water into inner and outer streams. Depending on the season, the proportion will always before 4:6.
The "head" of Dujiangyan with the "islands" and the levee...
The expanse of man-made islands breaks down the strong flow of the current,
resulting in a curious flow at the Fish Head Levee...
(Note the flow of the water upon hitting the levee)
resulting in a curious flow at the Fish Head Levee...
(Note the flow of the water upon hitting the levee)
The Waijiang Floodgate controls the flow of water to the Outer Stream...
Flying Sand Weir (飞沙堰)
The Flying Sand Weir (飞沙堰) has a 200 m-wide opening that connects the inner and outer streams. This further safeguards against flooding by allowing the natural swirling flow of the water to drain out the excess water from the inner to the outer stream. The swirl created also sieves out the silt and sentiment to prevent it clogging the inner stream. This debris is then excreted into the outer stream. A modern reinforced concrete weir has replaced Li Bing’s original weighted bamboo baskets.
Merlion Wayfarer finds this portion the most ingenious, as the inventor actually thought of expelling the debris and sediment back to the fastflowing river using a system of rocks to filter these out...
Bottle-Neck Channel (宝瓶口)
The Bottle-Neck Channel (宝瓶口), which Li Bing gouged through the mountain, is the final part of the system. The channel distributes the water to the farmlands to the west, whilst the narrow entrance, that gives it its name, works as a check gate, creating the whirlpool flow that carries away the excess water over the Flying Sand Fence, to prevent floods.
The other components of Dujiangyan as viewed from Qinyan Tower...
A distant pagoda in the Outer Stream...
