The present structure of the dam
|Official name||Kallanai Dam|
|Location||15 km from Tiruchirappalli, Tamil Nadu|
|Dam and spillways|
|Type of dam||Composite Dam and Reservoir|
|Length||0.329 km (1,079 ft)|
|Base width||20 m (66 ft)|
Kallanai (also known as the Grand Anicut) is an ancient dam built across the Kaveri River in the state of Tamil Nadu in South India. Located at a distance of 15 km from Tiruchirapalli, the dam was originally constructed by the Chola king Karikala around the 2nd Century AD. and is considered to be one of the oldest water-diversion or water-regulator structures in the world which is still in use. It still stands as a symbol of Dravidian Engineering.
The dam was originally built by Karikala Chola around first century AD. The idea behind constructing the dam was to divert the river to the delta districts thereby boosting irrigation. The dam was re-modeled by the Britishers during the 19th century AD – In 1804, captain Caldwell, a military engineer was appointed by the British to make a study on the Kaveri river and promote irrigation for the delta region. He found that a large amount of water passed onto the Kollidam leaving behind a small volume for irrigation purposes. Caldwell initially proposed a solution by raising the dam and hence raised the dam stones to a height of 0.69 m, thus increasing the capacity of the dam. Following this, Major Sim proposed the idea of undersluices across the river with outlets leading to the Kollidam River (Coleroon) thus preventing formation of silt. The Lower Anaicut built by Sir Arthur Cotton in 19th century AD across Coleroon, the major tributary of Cauvery, is said to be a replicated structure of Kallanai.
The Kaveri river splits into two at a point 20 miles (32 km) west of Kallanai. The two rivers form the island of Srirangam before joining at Kallanai. The northern channel is called the Kollidam (Coleroon); the other retains the name Kaveri, and empties into the Bay of Bengal at Poompuhar. On the seaward face of its delta are the seaports of Nagapattinam and Karaikal.
The purpose of the Kallanai was to divert the waters of the Kaveri across the fertile delta region for irrigation via canals. The dam splits the river Kaveri into 4 streams known as Kollidam Aru, Kaviri, Vennaru and Puthu Aru. It is constructed from unhewn stone spanning the Kaviri and is 329 m (1,079 ft) long, 20 m (66 ft) wide and 5.4 m (18 ft) high. The dam is still in excellent repair, 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 area irrigated by the ancient irrigation network is about 69,000 acres (27,900 ha). By the early 20th century, the irrigated area had been increased to about one million acres.
The Delta farmers of Tamil Nadu have demanded that the Tamil Nadu government honour Karikala Cholan, who built the Kallanai.
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