Periyar, , (meaning: big river) is the longest river and the river with the largest discharge potential in the Indian state of Kerala. It is one of the few perennial rivers in the region and provides drinking water for several major towns. The Periyar is of utmost significance to the economy of Kerala. It generates a significant proportion of Kerala's electrical power via the Idukki Dam and flows along a region of industrial and commercial activity. The river also provides water for irrigation and domestic use throughout its course besides supporting a rich fishery. Due to these reasons, the river has been named the "Lifeline of Kerala". Kochi city, in the vicinity of the river mouth draws its water supply from Aluva, an upstream site sufficiently free of seawater intrusion. Twenty five percent of Kerala's industries are along the banks of river Periyar. These are mostly crowded within a stretch of in the Eloor-Edayar region (Udhyogamandal), about north of Kochi harbor. Origin and path The Periyar has a total length of approximately and a catchment area of , of which is in Kerala and is in Tamil Nadu. Sources The source of the Periyar lies high in the Western Ghats. The state of Kerala asserted during the hearings on the Mullaperiyar issue in the Supreme Court of India that the Periyar originates in Kerala, flows entirely through Kerala and joins the sea in the Kerala. This was also admitted by the state of Tamil Nadu in the court. Periyar originates at the southeastern border of Idukki district. The source of the river lies in the remote forests of the Periyar Tiger Reserve. The river originates from Chokkampatti Mala, a peak on the southern boundary of the Periyar Tiger Reserve. Course In its early course, the river flows in a narrow north sloping valley starting from the Chokkampatti hills and extending north about , with a number of sharp lateral ridges running down to it from east and west. After flowing from its origin and on reaching Mount Plateau at its eastern end, it is joined by the west-flowing Mullayar—an important tributary—at Mullakudy. During this journey the Periyar traverses through the Periyar Tiger Reserve, flowing across or forming the boundaries between various sections of the reserve. Going downstream, it defines a part of the border between Periyar section of the reserve in the east and Sundaramala section in the west and