Kallanai is built on the river of Cauvery in the state of Tamil Nadu. Kallanai is known as Grand Anicut built by the chola king Karikalan around the 1st century AD.Kallanai dam in tiruchi is considered to be one of the oldest water-regulator structures in the world that is still in use.

Kallanai is a Tamil word which means stone dam. Kallanai in tiruchi is a massive dam of unhewn stone which is of 329 meters long and 20 meters wide, built across the main stream of the river Cauvery.

This dam breaks into two channels at the island Sri Rangam. The northern channel is called kollidam and the other is the same name as Cauvery and this empties into Bay of Bengal at poompuhar.

This dam was basically planned only for the sorage of water, later it was fitted with gates to divert the stored waters of Cauvery across fertile delta region for irrigation. The area irrigated by this ancient irrigation network is about 69,000 acres which is increased to about 100000 acres by the early 20th century.

This dam is still in a good condition and has stayed as a model to later engineers including Sir Arthut Cotton’s dam across kollidam, the major branch of river Cauvery.