The Periyar River is the longest river in the state of Kerala, with a length of 244 km.
it is known as The lifeline of Kerala.
The Idukki Dam on the Periyar generates a significant proportion of Kerala's electrical power.
It flows north through Periyar National Park into Periyar Lake.
Its largest tributaries are the Muthirapuzha River, the Mullayar River, the Cheruthoni River, the Perinjankutti River and the Edamala River.