Periyar (பெரியாறு/Malayalam: പെരിയാര്‍ meaning: big river) is the longest river in the state of Kerala, India, with a length of 244 km. The Periyar is known as the lifeline of Kerala; it is one of the few perennial rivers in the region and provides drinking water for several major towns.The Idukki Dam on the Periyar generates a significant proportion of Kerala's electrical power

[edit]Origin and Path

Periyar river view at Bhoothathankettu near Kothamangalam, Ernakulam.

Periyar originates in the Sivagiri hills of the Western Ghats range at the border of Tamilnadu and Kerala. It flows northwards for 48 kms and at Thekkady joins the west-flowing Mullayar, also originating in the Western Ghats in Kerala. The Mullaperiyar dam is constructed at the confluence of both the rivers Periyar and Mullayar to create the Periyar lake and reservoir and the Periyar National Park.

From Periyar Thekkady lake and reservoir, water is diverted eastwards to Tamilnadu via a tunnel enabling the water to join the Vaigai River. From Periyar Thekkady Reservoir, the Periyar river flows northwestward for 35 kms through Vandiperiyar, Elappara and Aiyyappankoil to join the Idukki reservoir formed by the Idukki, Cheruthoni and Kulamavu dams. From Idukki reservoir, Periyar river flows northwestwards and then westward to join the Arabian sea at Munambam near Kodungallur and the Vembanad lake at Kochi.

[edit]Tributaries

Its major tributaries are:

• Muthirapuzha River
• Mullayar River
• Cheruthoni River
• Perinjankutti River
• Edamala River

Minor tributaries are: Muthayar, Perunthuraiar, Chinnar, Cheruthony, Kattappanayar

[edit]Hydro electric projects

The largest hydro- electric project of the state, namely Idukki with its arch dam is on this river. Pallivasal, Chenkulam, Panniyar, Neriyamangalam and Lower Periyar are the other hydro electric projects on river Periyar.

[edit]Dams

Mullaperiyar, Bhuthathankettu, Mattupetty, Munnar, Idukki,Cheruthoni, Kulamavu, Irattayar, Lower Periyar, Edamalayar, Chenkulam, Anayirangal and Ponmudi are the important dams across this river.

At Aluva, the river bifurcates into the Marthandavarma and the Mangalapuzha branches. The Mangalapuzha branch joins Chalakkudy river and empties into the Lakshadweep sea at Munambam, and the Marthandavarma branch flows southwards, through the Udhyogamandal area and joins the Cochin backwater system (part of Vembanad Lake) at Varapuzha.

[edit]The Idukki Dam

Idukki Dam across the Periyar river

The Idukki Dam on the Periyar is the biggest dam of its kind (a concrete, double curvature parabolic, thin arc dam) in Asia and the second biggest in the world. Its generators have a power output of 780 MW (6 X 130), and generate electricity through the underground Power House facility at Moolamattam, built by an India-Canada Joint Venture. Power generation at Idukki is minimal during the monsoon. The dam also permits storage of water for the dry summer period when many other reservoirs in the area are low.

[edit]Pollution

The lower reaches of the Periyar are heavily polluted. Industries in the Eloor industrial zone discharge waste into the river. Greenpeace India describes the lower Periyar as "a cesspool of toxins, which have alarming levels of deadly poisons like DDT, endosulfan, hexa and trivalent chromium, lead,cyanide, BHC."