Kollidam Riveralso called Coleroon Riverriver, east-central Tamil Nadu state, southeastern India. Formed by the northern bifurcation of the Kaveri (Cauvery) River at just west of Srirangam, the Coleroon Kollidam River flows between the South Arcot and Thanjavur regions for 36 miles (58 in an easterly and then northeasterly direction for about 95 miles (150 km) and empties through several mouths into the Bay of Bengal 3 miles (5 km) south of Porto Novo. The Coleroon is part of the Kaveri deltaroughly equidistant between the Puducherry (north) and Karaikal (south) sectors of Puducherry union territory on the coast. The Kollidam is the major northern stream of the Kaveri delta. The river was dammed in 1836 to help provide irrigation water for the delta, the most fertile and densely populated region of southern India, noted for its rice production. The town of Chidambaram lies on its banks.