Grand Anicut - Kallanai - Oldest Barrage in the World
Kallani, also known as Grand Anicut is one of the oldest water diversion or water regulatory structure in the World, which is still in use in excellent condition. In Tamil, 'Kal' means Stone, 'Anai' means Dam. This Anicut is more than 2000 years old, built by the Great King 'Karikala Cholan' of Chola Dynasty, during 100 B.C.
It is a massive barrage of unhewn stones about 1080 feet long, 18 feet high and 60 feet wide built across the holy river Cauvery in Tiruchirapalli district of Tamil Nadu. The main reason for building this engineering marvel was to divert water to the fertile agricultural lands via canals and to avoid loss of crops during floods. It has irrigated around 69,000 acres of agricultural lands, when it was built.
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| Distant View of Kallanai |
History behind Kallanai
When the great king Karikala Cholan ruled Southern India, people from Cauvery delta region has suffered from two extremities of nature. During Rainy season, this region has experienced floods, which extremely devastated agricultural lands and during summer season it experienced droughts. To strike a balance of water, the King has come up with the idea of Grand Anicut, which will provide steady flow of water throughout the year for irrigation.
During flood times, the excess water will be passed to Kollidam river through ullar river. Kollidam - in Tamil 'Kol' means to contain and 'Idam' means place, the place that can contain more water, as the name says it can actually contain about 4 lakh cusecs of water.
The Cauvery river splits into two channels, the Northern channel is called 'Kollidam' and Southern channel retained the name 'Cauvery', which will further flows to Bay of Bengal at Poompuhar junction. The king built this Grand Anicut at Southern channel. During floods it will be diverted from Cauvery branch of river to Kollidam branch and kollidam flowed directly to Bay of Bengal causing minimal damage to the agriculture. Kollidam was barely used for irrigation, it is more wider, steeper and faster.
The above picture is the top view of Grand Anicut / Kallanai. In this picture, you could see the Cauvery river flowing widely at the center and the water being diverted through this Anicut. Excess water is getting diverted into 4 smaller streams and canals were built from the streams for irrigation.
Leftmost part (Red Mark) - From this canal of the Anicut, Cauvery water flowing towards Uyyakondan suburb. This canal travels up to 70 Km and irrigates about 32,000 acres of land.
Second canal from left red mark - This canal from anicut flowing towards pattukottai district which covers about 46 kilometer
Third from the left (Center) - This canal is called as Vellar river flowing towards Tanjore /Thanjavur city, which contributes to the major rice production in South India.
Fourth from left (Center big) - Diverted Cauvery flowing towards Kumbakonam, Mayiladuthurai districts
Fifth from left (Right most) - Kollidam, excess water getting merged with kollidam river, which in turn reaches to Bay of Bengal .
Also, right most part of this Anicut is for flood / excess water, the excess water is getting diverted to Kollidam River.
Design
Building a strong engineering structure in middle of ferociously flowing Cauvery River was extremely arduous and requires skillful technicians. Our brilliant architects used natural approach to raise this barrage, that is Sand Erosion. They didn't control the nature with force. They sophisticatedly reshaped river water currents and the sedimentation process.
River Cauvery
It is a normal phenomenon experienced in beaches, when we stand in the beach, the sand below our feet will be eroded, the longer you stay, more the sand will be eroded, which moves you further into the water. Using this method, large blocks of granite stones were dropped into the river, when the stones moved under, insoluble binding material was used to place another stone over that. By the erosion process, the stones were positioned correctly and naturally formed a strong sand bed. This sand bed gave great strength and durability to the dam.
Massive boulders, rocks and unhewn stones were carried from mountains and directly sunken in the path of Cauvery river. The strong foundation of this barrage helped in raising this structure with four different canals to divert water to various regions.
Due to this Anicut, Thanjavur has turned into a Rice bowl of South India. 80 % population in Thanjavur is engaged in agriculture and this city is the important agriculture center of Cauvery Delta Region.
In 20th century, this Anicut has been raised to release water for irrigation to about 1 million agricultural lands lands .
This area was irrigated by ancient irrigation system, of which Kallanai was the centerpiece. It is believed that floods to an extent of 1,86,00 cusecs of water have been discharged through this Anicut with no damage.
Actually Kallanai is not a dam, it is one of the oldest water diversion and water regulatory structure in the world. The main purpose of building this engineering marvel across Cauvery River is, divert water to the agricultural lands for irrigation and to control floods during natural disaster.
Later, during British period, they raised the height of the barrage to 27 inches, to increase the capacity of the dam for the irrigation purpose. At the base of this structure, under-sluices were built across the river with outlets that leads to Kollidam river. This in turn prevented formation of silts, while diverting large amount of water.
When the western science was not evolved, this marvelous piece of hydraulic structure was built across a might Cauvery river with strong sand bed. This Indian engineering structure is one of the masterpiece in World's history !!!
-Aarthi Thiyagarajan
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