The construction of this Dam commenced on 30 April 1969. Storage of water in idukki reservoir commenced in February,1973. The inauguration of trial run of the first machine was celebrated on 4th October,1975. Commercial operation of the Power Station was Commissioned on 12 February 1976 by the then Hon. Prime Minister Smt. Indira Gandhi.
Construction of this Arch Dam and two other dams at Cheruthony and Kulamavu has created an artificial lake of 60 sq. kms. width and the water stored, is utilised for production of electricity at the unique Moolamattom Power house, which is located inside the rocky caves.The Project harnesses a major portion of the power potential of Periyar, the largest river in Kerala State, by the creation of a reservoir of 2,000 M.cum (2 Billion Tonnes) capacity, diversion of waters thus impounded through a water conductor system consisting of a power tunnel and two underground pressure shafts to an underground power house situated in Muvattupuzha Valley. The installed capacity of the Power House is 780MW consisting of 6 Units of 180 MW each.The regulated waters of Periyar falls through a drop of about 669.2 metres (2195 feet) while generating power in the underground power house.
The tail waters flowing to Kudayathurpuzha through tunnel and open channel will later be diverted for irrigation purposes in the Muvattupuzha Valley.
After 34 years , now the government of Kerala has decided to the maintenance of the Dam and the tunnel to the Moolamattom Power house for two weeks starting from 07.06.2009. During this period the Electricity generation will be stopped till the maintenace is over. Goverment has declared a load shedding from 07.06.2009 during the peak hours.
From Cochin in Kerala we can fetch many buses going to Kattapana or idukki. You can also hire a tourist vechicle to reach here.one of the important tourist