The Grand Anicut Dam, India's oldest at 2000 years!

S Balakrishnan *

India can boast of having one of the four oldest irrigation systems in the world that is still functional! The Kallanai / Grand Anicut dam is also India’s oldest irrigation structure! It was built in the 2nd century (150 AD) across River Cauvery near Thanjavur in Tamil Nadu by the Chola dynasty king Karikalan.

The idea was a multi-purpose one -
to divert flood waters into Kollidam branch of Cauvery to prevent flooding of the delta region;
better management and usage of the waters of Cauvery across the fertile Thanjavur delta area, the rice bowl of Tamil Nadu;
to check siltation of Kaveripoompattinam (Puhar/Poompuhar), the port town, that impacted sea trade;
to arrest the port area turning into a marshy wetland;
to commemorate his epoch-making victory in the Venni war,
a new canal was created at the check dam point and named Venni Aaru (aaru=river) that is today called Vennar;
to create permanent water transport facility to his capital city Uraiyur.

The barrage was built of massive, unhewn stones (rocks) on the sand bed of Cauvery, hence the name kal (stone/rock) anai (dam). Kallanai is more than 329 meters (1080 ft.) long, 20 meters (66 ft.) wide, and 5.4 meters high.

It was initially designed to irrigate 69,000 acres but by 1800 AD it was irrigating 6,00,000 acres, and is now irrigating 10,00,000 acres. Researchers believe that the dam, as built by King Karikalan, had some new, strange architectural ideas like the curved masonry portion with an irregular drop from front to rear and a slanting top. From Grand Anicut, Cauvery flows north-east and the Vennar, south-east.

The Kallanai was mainly constructed with the aim to divert flood waters of Cauvery/Kaveri branch of the river into the Kollidam branch of the river with the help of a short connecting stream; this will happen when the water level in Kaveri river rose above the top limit.

This was because Kollidam river is not only at a lower level but also wider than Cauvery, steeper, straighter and hence faster; therefore, the flood carrier, it was decided. Thus Cauvery became the lifeline of Thanjavur delta region while Kollidam was reduced to the level of flood carrier. Karikalan also constructed/strengthened the embankment of Cauvery River from Puhar (Kaveripoompattinam) to Srirangapatnam, spreading to 1080 ft.

Since the arrival of the British in Thanjavur by the end of 18th century (1799 AD), Kallanai has seen many changes; other hydraulic structures have been added nearby and tampered with iron sluice gates, etc.

Hence it is really difficult to visualise the original construction or working of the anicut (anai-k-kattu in Tamil is dam). Struck by the engineering marvel, the British called it Grand Anicut! Sir Arthur Cotton improved and strengthened it during 1835-36.

The original dam is so strong that a two-lane road is functional on the top of the dam since 1839 built over 30 arches of 32 ft. span each; thousands of Light Motor Vehicles daily ply either way. After modifications, the functionality of the barrage has improved a lot.

Recently, efforts have been initiated to modernise the 636-km-long Grand Anicut Canal System. It will improve irrigation facilities for 2.27 lakh acres of land.

As pointed out by Prime Minister Shri Modi, “For thousands of years, this Grand Anicut and its canal systems have been the life-line of the rice bowl of Tamil Nadu. The Grand Anicut is a living testimony to our glorious past. It is also an inspiration to our Nation’s Aatmanirbhar Bharat goals.