The Grand Anicut, also known as the Kallanai (kall -stone, anai-bund), is an ancient dambuilt on the Kaveri River in the state of Tamil Nadu in southern India. It is located about 20 km from Tiruchirapalli. It was built by the Chola king Karikala Chola around the 2nd Century AD and is considered 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 Ancient Engineering.
The Kaveri River forms the boundary between the Erode and Salem districts. The Bhavani River joins the Kaveri at the town of Bhavani, where the Sangameswarar Temple, an important pilgrimage spot in Tamil Nadu,was built at the confluence of the two rivers. Sweeping past the historic rock of Tiruchirapalli,it breaks into two channels at the island of Srirangam, which enclose between them the delta of Thanjavur (Tanjore), the garden of Tamil Nadu. The northern channel is called the Kollidam (Kolidam);the other preserves the name of Kaveri, and empties into the Bay of Bengal at Poompuhar, a few hundred miles south of Chennai (Madras).On the seaward face of its delta are the seaports of Nagapattinam and Karaikal.Irrigation works have been constructed in the delta for over 2,000 years.
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(28,000 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