river of Karnataka (Karnātaka) and Tamil Nadu (Tamil Nādu) states, southern India. It rises as the Southern Pinakim on the eastern slope of Nandidrug Mountain, in the Chennakaseva Hills of eastern Karnataka. It then flows southward for 50 miles (80 km) through Karnataka to northwestern Tamil Nadu, where it turns southeastward and flows 200 miles (320 km) to enter the Bay of Bengal (Bengal, Bay of) at Cuddalore. Major tributaries are the Chinnar, Markanda, Vaniar, and Pamban. Heavy rains at the river's source cause sudden, but short-lived, floods. The river is extensively dammed for irrigation, especially in Tamil Nadu. There are also reservoirs at Krishnagiri and Sathanur. The Ponnaiyar is considered sacred by Hindus, and festivals are held during the Tamil month of Tai (January–February).