Idukki Project
The Idukki hydroelectric project is located on the Western Ghats of the Indian Peninsula at an altitude of 695 metres above the sea level. The reservoir is formed by three dams-- an arch dam across the Periyar River and a concrete dam across the Cheruthony River and a masonry dam at Kulamavu, upstream of Idukki. The reservoir covers nearly 60 square kilometres and has a catchment of 649 square km. Water from the reservoir is taken down to the underground powerhouse at Moolamattom through an underground tunnel, yielding an average gross head of 2182 feet (665 metres). The project has an installed capacity of 780 MW with firm power potential of 230 MW at 100 per cent load factor.
The project involved diversion of the waters of upper part of Periyar into the Muvattupuzha River. This caused severe drought in areas down stream of the river in summer and reduced fresh water availability for industries located near the mouth of the river. The fresh water regime of Periyar River was in dynamic equilibrium with the estuarine tidal cycle. The impoundment of the dam and diversion of water upset this equilibrium. This led to saline water intrusion into areas where fresh water was available previously.
After impoundment of the dam, hundreds of tremours had been recorded in the Idukki area and most of them are classified as reservoir induced. So far, these tremours have not caused any serious damage. Valley slumpings and slope failures became more common in the area following construction of the dam. A major reason for this was the destruction of the forests during and after the construction. The project opened up the inner forests of Idukki district. This accelerated migration to the area, with the work force of around 6000 itself acting as the nucleus.
The project submerged about 6475 hectares of evergreen and deciduous tropical forests. Besides, the construction of roads, cutting of trees and encroachments led to loss of about 2700 hectares of forests and degradation of the remaining forests. Much of the degradation of forests that has happened over the years is irreversible. Owing to loss of habitat, some reptilian species like the rare terrapin has become extinct or sparse.
The reservoir attracted some species of birds, but the number of some other species went down. During the 1975-1983 period (the first phase of the Idukki project was commissioned in 1976), dense vegetation cover in the surrounding areas went down by 56 per cent and sparse vegetation cover by 37 per cent. The area under agriculture increased by 126 per cent. (These indicate the extent of encroachments that had taken place over the years).
Though the area of forests enfolded by the reservoir was declared a wildlife sanctuary as a mitigative measure, it did not help much in conserving the larger herbivores. It has even been recommended that the sanctuary be denotified as the area is not sufficient for meaningful conservation of wildlife.
The project required the eviction of 759 households (population 4500) including tribals. The impacts on the tribals were similar to that faced by the Cree in the James Bay territory. The tribals originally formed an integral part of forests. Their main occupations were hunting, collection of minor forest produce and shifting cultivation. They lived in simple huts made of materials available in the forests. They were rehabilitated in modern houses. This made them sedentary and forced them to abandon their traditional occupations. Their simple way of life had to give way to modern lifestyle and consumption patterns.
Idukki was proposed as a multi purpose project. The objectives included flood control, pisciculture, forestry, horticulture, tourism development, inland water transport and water for domestic and industrial use. As in the case of James Bay (with regard to mining, forestry etc.), hardly any of these materialised.
Idukki was proposed as a multi purpose project. The objectives included flood control, pisciculture, forestry, horticulture, tourism development, inland water transport and water for domestic and industrial use. As in the case of James Bay (with regard to mining, forestry etc.), hardly any of these materialised.
Effectiveness of Mitigation Measures
In the case of Idukki project, hardly any mitigative measures were undertaken other than efforts by Government agencies to check encroachment and conserve the forests close to the reservoir. But these proved ineffective to a large extend. However efforts to check erosion by planting trees were somewhat effective when attempted properly. This, however, proved to be costly because of wastage of funds and corruption.
The experience with the James Bay Project shows that mitigative measures had their limitations. They proved to be expensive and only marginally effective. It was found that preventive measures were better than mitigative measures. According to the developers themselves, it was ten times easier and cheaper to preserve a habitat from damage than to restore it after damage.
Hydro Quebec has, however, gained much experience and developed certain methods and technologies to manage power projects better. Decisions taken early, while optimising design, regarding major aspects like river diversions, design and location of dams, dikes and tailrace canals were found to avert significant damage. Dikes, for example, have helped to protect productive riparian habitat, valleys and lakes from flooding and erosion. Some of these experiences and technologies could be useful for future projects in India.
Certain impacts like mercury pollution at James Bay and reservoir-induced seismicity in Idukki were unanticipated. And no remedy could be found for them. This highlights the uncertainties associated with the impacts of hydroelectric projects.
Idukki has an area of 5,105.22 km² (1,971.1 sq mi) and is the second largest District of Kerala. Rugged mountains and forests cover about 97 percent of the total area of the District. The district borders the Kerala districts of Pathanamthitta to the south, Kottayam to the southeast, Ernakulam to the northeast and Thrissur to the north and Coimbature, Dindigul and Theni Districts in Tamilnadu to the east.
Anamudi, the highest peak in India south of Himalayas, is in the Kuttampuzha Panchayat of Adimali Block, in the K.D.H Village of Devikulam taluk. 13 other peaks in the district exceed a height of 2,000 m (6,562 ft). The Periyar, Thodupuzhayar and Thalayar are the important rivers of the district.Idukki has an area of 5,105.22 km² (1,971.1 sq mi) and is the second largest District of Kerala. Rugged mountains and forests cover about 97 percent of the total area of the District. The district borders the Kerala districts of Pathanamthitta to the south, Kottayam to the southeast, Ernakulam to the northeast and Thrissur to the north and Coimbature, Dindigul and Theni Districts in Tamilnadu to the east.
In the heart of the District lies the 'IDUKKI DAM' - Asia's biggest Arch Dam of 555 feet height proudly standing between the two mountains - 'Kuravanmala' (839 meters) and 'Kurathimala' (925 meters ). This prestigeous project of our nation is situated in Idukki District and its underground Power House is located at Moolamattom which is about 19 kms from Thodupuzha. Idukki Dam is 43 kms away from Moolamattom.
History
The possibility of Hydroelecric development at Idukki was first conceived in 1919. As per history Shri Kolumban, the head of 'Araya' race during 1922 showed the way, to the Malankara Estate Superintendent and his friend Thomas, who were on hunting spree in the forest, the spot of present Arch Dam. He told them of the legend of Kuravan and Kurathi Hills. The mind of Thomas was stirred by the sight of water flow between the mountains and his idea made the dream true of Idukki Arch Dam. Sri. W.J.John of Malankara Estate submitted a report to the Government of Travancore in 1932 on the possiability of constructing a dam at Idukki for Power Generation.
In 1947 Sri.P.Joseph John,then Chief Electrical Engineer to the Government of Travancore made a preliminary investigation report. On the request made by the Government, the Central Water and Power Commission took up detailed investigation in 1956. The project report was prepared in 1961 and the Planning Commission accorded sanction for implementing the scheme in 1963 and the preliminary works of the project were started. The project was posed for Canadian aid and its scope was enlarged and a revised project report was drawn up in 1956-66.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.Foreign Aid
The Government of Canada aided the Project with long term loans and grants. M/s S.N.C.Inc., Canada, a well-known firm of Consulting Engineers were advising and assisting Project Engineers under the Canadian Aid.Project in Brief
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.
