The dam was originally built by Chola dynasty King Karikalan in c. 100 BC — c. AD 100. It is located in the district of Tiruchirapalli, on the river, about 20 km from Tiruchirapalli city. The idea behind the dam construction was to divert the river towards the delta districts, thus boosting irrigation. During the 19th century the British re-modelled the dam. In 1804 the British appointed Captain Caldwell, a military engineer, to conduct a study on the Kaveri River and to promote irrigation for the delta region. He noticed that for irrigation purposes, a large amount of water flowed onto the Kollidam leaving behind a small volume.Caldwell originally suggested a solution by raising the dam and thus raised the dam stones to a height of 69 centimetres (27 in), thereby increasing the capacity of the dam. Major Sim subsequently suggested the concept of undersluices running across the river with outlets leading to the Kollidam River (Coleroon) thus preventing silt formation. The Lower Anaicut, founded in 19th century CE by Sir Arthur Cotton across Coleroon, Cauvery 's main tributary, is said to be a replicated Kallanai building.
The purpose of the Kallanai was to divert the waters of the Kaveri across the fertile delta region for irrigation via canals and to its northern delta branch Kollidam. The Kaveri River splits downstream of the dam into four streams known as Kollidam Aru, Kaveri, Vennaru and Puthu Aru. It is made of unhewn stone spanning the Kaveri and is 329 m (1.079 ft ) long, 20 m (66 ft) wide and 5.4 m (18 ft ) high. By opening the barrage / anaicut gates, the flood waters can be allowed to pass through the other three delta branches also to join the sea.The dam is still in excellent condition, and supplied a model to later engineers, including Sir Arthur Cotton's 19th-century dam across the Kollidam, the major tributary of the Kaveri. The region irrigated by the ancient irrigation network is around 69,000 acres (28,000 ha). The irrigated area had been increased to about one million acres by the early 20th century. Tamil Nadu 's delta farmers have demanded that the government of Tamil Nadu honor Karikala Cholan, who built the Kallanai.