Sketch Map & Introduction to Dujiangyan Weir
A: Fish Mouth.
B: Outer River Dike (Jingang Dike).
C: Inner River Dike (Jingang Dike).
D: Inner River.
E: Outer River.
F: Mingjiang River.
G: Feishayan (Drainage Dam).
H: Renzi Dyke.
I: Bottle Mouth.
J: Lidui Park.
K: Baizhang Dyke (Dike).
L: Erwang Temple.
In Minjiang River, the annual flux up to 15 billion cubic meters, and
about 40 million tons of sands and stones washed down from upper
reaches. Flood burst out frequently, in 256 BC, the governor of the Shu
Prefecture (now as Sichuan area) organized local people to build the
greatest project, and till now it works very well.
The Sichuan people summarized its experience in flood
control and water usage as: "Harnessing Shoals Deep, Building Dams
Lower" or "Keep the weirs low and the sluices deep".
Fish Mouth (Yuzui in Chinese), located in the upper
middle (the heart point close to the bend of the river) of Minjiang
River (as "A" in the sketch). The Fish Mouth dyke divide the river into
2 flows: the inner river (D) and outer river (E), with wide for outer
river (with little higher river bottom) to keep more flux (60%) into
outer river if rainy season and keep few flux (40%) into outer river if
non-rainy season, as well as more sands and stones into outer river,
narrow for inner river (with little deeper river bottom) to keep certain
amount of flux to into inner river.
Bottle Mouth (Baobingkou), the bottom width 14.3M, the
top width 28.9M, height 18.8M, water width 19M at lower water and 23M at
its flood water. It divide and control the water again to keep water
into irrigated canal for Sichuan irrigation.
Feishayan (drainage dam, training banks), width 240M with 2 meters
height. About 710M to Yuzui and 200M to Baopingkou. If in flood season,
the flows to the bank (upper) and then return to this dam, and carry
sands with stones across the dam into outer river with large flux. And
this dam was built with bamboo cages filled with cobblestones for a long
time in history.
In this project, there is no really dam, but only lower dyke to keep the water flows naturally with different direction to different way, never to break the flow with a high dam. Every year there is a annual reconstruction (just as: carry the sands out of the river bottom), then no any other environment problem such as Dam broken, sedimentation and erosion etc.