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. Since the commissioning of the Idukki project in 1976, tail-race water (between 19.83-78.5 m3/s) has been diverted from the Idukki reservoir through the Moolamattom power station into the Thodupuzha tributary of the Muvattupuzha river. There are other hydro-electric generation facilities on the river at Pallivasal, Chenkulam, Panniyar, Neriyamangalam and Lower Periyar. Reservoirs The important reservoirs in the Periyar basin within Kerala are Bhoothathankettu, Idamalayar, Lower Periyar, Mattupetty, Anayirangal, Kundala, Ponmudi, Kallarkutti, Idukki (formed by construction of three dams—Idukki, Cheruthoni and Kulamavu), Sengulam, Kallar, Erattayar and Mullaperiyar. The dams falling within Tamil Nadu in the Periyar basin are the Upper Nirar Weir and the Lower Nirar Dam. These dams help divert water from the Nirar tributary of Periyar to the adjacent Sholayar basin. Irrigation The Periyar valley Irrigation project in Ernakulam district envisages the utilization of the tail race discharge from the completed Hydel scheme in the Muthirapuzha tributary of river Periyar together with the controlled release from Ennackal dam constructed by Kerala State Electricity Board under Hydel scheme across the Idamalayar tributary and the dependable run off from the uncontrolled catchment of Periyar river, for irrigating an area of of land lying on the left bank of Periyar river through a network of canal system and controlling devices. The scheme consists of the Periyar Barrage at Bhoothathankettu with a catchment area of along with a network of canals. Apart from irrigation on left bank of Periyar, the project also enables a supply of minimum quantity of water through the river to check the intrusion of salinity at lower reaches of the river as well as to meet the requirements of many lift irrigation schemes of river Periyar. Supply of water for drinking and industrial purposes are met by a portion of storage water by the barrage of Bhoothathankettu. Inter-basin transfer of water Mullaperiyar dam was one of the earliest instances of inter-basin transfers in the peninsular India. While it met the demand for water on one hand, it led to the deterioration of water quality downstream of the river. Salinity intrusion and pollution dispersion problems arose in the lower reaches of the Periyar due to non-availability of sufficient quantity of water for flushing. Another