Monday, July 7, 2008
Tehri dam is the main dam of the Tehri Hydro Project, a major power project located near Tehri in the state of Uttarakhand in India. It is a multi purpose river valley project.Towering 855 feet (261 m), the main dam at Tehri is the 8th tallest dam in the world.The dam's projected capabilities include a power generation capacity of 2400 MW, irrigation stabilization to an area of 6,000 km², an additional area of 2,700 km² of irrigation stabilization and a supply of 270 million gallons (1.23 million cubic metres) of drinking water (per year?) to industrialized cities in Delhi, Uttar Pradesh and Uttarakhand. While originally stated to be built with an approximate cost of 4 million U.S. dollars, an equivalent of over 1 billion US dollars has been spent on the construction of the dam to date.
The dam project was approved in 1972 and construction was started in 1978. The Tehri Hydro Development Corporation (THDC) was constituted in 1989 to supervise the construction of the dam. The main dam of the project is built near the old Tehri town that lies at the confluence of the rivers Bhagirathi, (one of the major tributary of the river Ganga) and Bhilangana. The main dam will produce 2000 MW of electricity when completed. However, only the Phase-I with capacity of 1000 MW is approved at present. There is another smaller dam 14 km downstream at Koteshwar that will produce 400 MW of electricity. The main reservoir comprises an area of 42 km². This has now flooded the old Tehri town and 112 villages around the town, thereby displacing more than 100,000 people. The town of New Tehri, on the hillside above the dam, has been built as a result.
This dam has been the object of intense protests from environmental groups and the people of this region. The issue of relocation of more than 1 lakh (100 thousand) people of the area has resulted in protracted legal battles and has delayed the project. Besides this, environmental concerns regarding the location of large dams in the fragile ecosystem of the Himalayan foothills, there are also concerns regarding the dam's safety. The Tehri dam is located in the Central Himalayan Seismic Gap, a major geologic fault zone. This region was the site of a magnitude 6.8 earthquake in October 1991, epicentred 50 km from the location of the dam. There already has been a fatal accident in one of the tunnels in Aug, 2004 when a portion of a tunnel collapsed following heavy rains.
Following a court clearance, the tunnel T2 of Tehri dam has been finally closed on 29th Oct, 2005 and thereby started the process of filling the massive reservoir. Its planned closure was in Dec, 2002. Two of the lower tunnels, T3 and T4, were closed way back in Dec, 2001. But closing of tunnel T2 has resulted in another controversy as this has reduced supply of Bhagirathi water to a mere 2 ft³/s from the normal 1000 ft³/s. According to Hindu mythology, river Bhagirathi is the actual Ganga, though the name of Ganga is assumed only after the river Bhagirathi meets river Alaknanda at Devprayag. Cutting off the water supply of Bhagirathi to such low quantity means that after travelling more than 80 km from this point, water of Bhagirathi will be hardly reaching Ganga. Thus to many, sacredness of Ganga has reduced and this has created resentment. But the filling of the dam continued and the project generated its first unit of electricity in June, 2006.