The Western Ghats form one of the four watersheds of India, feeding the perennial rivers of India. The major river systems originating in the Western Ghats are the Godavari, Kaveri, Krishna, Thamiraparani and Tungabhadra rivers. The majority of streams draining the Western Ghats join these rivers, and carry a large volume of water during the monsoon months. These rivers flow to the east due to the gradient of the land and drain out into the Bay of Bengal. Major tributaries include the Bhadra, Bhavani, Bhima, Malaprabha, Ghataprabha, Hemavathi and Kabini rivers. The Periyar, Bharathappuzha, Pamba, Netravati, Sharavathi, Kali, Mandovi and Zuari rivers flow westwards towards the Western Ghats, draining into the Arabian Sea, and are fast-moving, owing to the steeper gradient.