Coimbatore district is in the western part of Tamil Nadu, bordering the state of Kerala. It is surrounded by the Western Ghats mountain range on the west and north, with reserve forests and the (Nilgiri Biosphere Reserve) on the northern side. The Noyyal River runs through Coimbatore and forms the southern boundary of the old city limits. The city sits amidst Noyyal's basin area and has an extensive tank system fed by the river and rainwater. The eight major tanks/wetland areas of Coimbatore are Singanallur, Kallimadai, Valankulam, Ukkadam Periyakulam, Selvampathy, Narasampathi, Krishnampathi, Selvachinthamani, and Kumaraswami tanks. Sanganur pallam, Kovilmedu pallam, Vilankurichi-Singanallur Pallam, Karperayan Koil pallam, Railway feeder roadside drain, Tiruchy-Singanallur Check drain and Ganapathy pallam are some of the streams that drain the city.