Origin and Path

The Periyar river is the longest river in the state of Kerala, India, with a length of 244 km. The river is also known as The lifeline of Kerala as it is one of the few perennial rivers of Kerala. It provides drinking water for major towns.

The Idukki Dam has been built across the river and generates a significant proportion of electrical power for the state. This is a concrete, double curvature parabolic, thin arc dam.

The Periyar's source is in the Western Ghats range in the Kerala state. Periyar is one of the few major rivers in Kerala which flow completely within the state. It flows north through Periyar National Park into Periyar Lake, an artificial reservoir created in 1895 by the construction of a dam across the river. The lake has an area of 55 km². Water is diverted from the lake into the Vaigai River of Tamil Nadu via a tunnel through the Western Ghats.

From the lake, the river flows northwest through the village of Neeleswaram into Vembanad Lake and out to the Arabian Sea coast. Its largest tributaries are the Muthirapuzha River, Mullayar River, Cheruthoni River, Perinjankutti River and the Edamala River.

The Periyar is the major water resource for five drought prone districts of Tamil Nadu, including Theni, Madurai and Ramanathapuram. The dam is maintained by Tamil Nadu PWD (public works department) and it is leased by the Tamil Nadu government for 999 years according to a pact between the governments of Kerala and Tamil Nadu. This deal was made during the British raj, between Travancore kingdom and the British colonial rulers representing Tamil Nadu

In the later parts of its journey to the Arabian Sea, the Periyar becomes heavily polluted. Various industries in the Eloor industrial zone discharge their waste into it. Greenpeace India suggests that in this region the river has been turned into "a cesspool of toxins, which have alarming levels of deadly poisons like DDT, endosulfan, hexa and trivalent chromium, lead, cyanide, BHC.”