File:Periyar origin.jpg

English: Periyar originates from the Sivagiri hills of the Western Ghats range in Kerala. It flows north through Periyar National Park into Periyar Lake, a 55 km² artificial reservoir created in 1895 by the construction of a dam across the river. Water is diverted from the lake into the Vaigai River in Tamil Nadu via a tunnel through the Western Ghats. From the lake, the river flows northwest through the village of malayatoor, east cheranalloor, aluva, and into Vembanad Lake and out to the Arabian Sea coast. Its largest tributaries are the Muthirapuzha River, the Mullayar River, the Cheruthoni River, the Perinjankutti River and the Edamala River. Through the Periyar Lake dam and tunnel, the river serves as the major water source for five drought-prone districts in the state of Tamil Nadu, including Theni, Madurai and Ramanathapuram. The dam is maintained by the Tamil Nadu public works department under a 999-year lease arranged between the governments of Kerala and Tamil Nadu. This deal was made during the British Raj era, between the kingdom of Travancore and British colonial rulers representing Tamil Nadu.