The Dujiangyan Dam,45km north of Chengdu,is an ancient technological wonder of
the country.More than 2000 yers ago,Li Bing(250-200BC),as a local governor of
the Shu State,designed this water control and irrigation dam and organized
thousands of local people to complete the project to check the Mingjiang
River.For many years the river,flooded the Chengdu agricultural area and local
farmers suffered a lot from the water disaster.Due to the success of the
project,the dam automatically diverts the Mingjiang River and channels it into
irrigation canals.For many years the dam has continued to make the most of the
water conservancy works.
Expansion has been undertaken since 1949 and at present the system does a
good job of irrigating farming land across 33counties of the western part of
Sichuan Province.Local people feel proud of the system becaude it has supported
a large amount of people in their daily life.
What makes this system so good?
The system is a large hydraulic water project which consists of three main
parts:the Fish Mouth Water-Dividing Dam,the Flying Sand Fence,and the
Bottle-Neck Channel.
The Fish mouth functions to divide the flow of water into an inner river
and an outer river.Long ago,when Li Bing worked as the local governor of the
Shu State,he found the old river canal was too narrow to hold much water,which
often overflowed the banks and caused disastrous flood.Based on natural
geographic conditions,he organized the people to build a man-made dam.The
whole dam looks like a fish,and the front dam has a circular cone shaped like a
fish mouth.It is the dam that channels water into an outer canal and an inner
canal.The outer water canal functions as the main stream and holds sixty
percent of water in the river.The extra water goes through the inner canal for
irrigation in Chengdu areas.
The Flying Sand Fence joins the inner and outer canals.The fence functions
to controll the flow of water and discharge excess into the inner canal from the
main stream.During the dry season the fence doesn‘t work much,but when floods
occur,the river rushes forward along the outer canal.As it approaches the
fence,the fence,the river begins to turn round fast and soon many whirlpools
are formed.The volatile whirlpools sweep away sand and pebbles and,throw them
into the outer canal.For many years huge bamboo baskets were used as the fence.
They were filled with stones and pebbles.However,at present,reinforced
concrete weir has replaced the ancient fence.
So now,let‘s discuss the Bottle-Neck Channel.A trunk canal was cut
through the mountain into two parts which link up the inner canal for
irrigation.The small part is later called Li Dui,which means an isolated hill.
Chengdu looks like a large bottle and the trunk canal between the mountain and
the hill takes shape of the bottleneck.The trunk canal technically has two
functions:First,it leads the water to irrigate the farming land in western
Sichujan; Secondly,the trunk casnal works together with the Flying Sand Weir to
keep the flow below a certain point in the inner canal during flood season.Some
stone tablets,which stand on the isolated hill,are engraved in Buddhist
Sanskrit.The local people hope that the Buddhist tablets can exert the Buddhist
superpower to harness flood disaster.For over two thousand years,in fact,the
Fish Mouth Water-Dividing Dam,the Flying Sand Weir,and the Bottle-neck Channel
automatically work together to control foods and sweep away sand and stones in
the main stram.The local people benefit a lot from this project.