Power Point

Experts have given conflicting reports on the Tehri dam

 
Last Updated: Sunday 28 June 2015

Power Point

-- The Tehri dam project has always been embroiled in controversies. The initial protests against the dam started in the late 1960s when surveys were conducted at the dam site. An organised movement took shape after the Planning Commission gave its nod to the dam in 1972. In the 1980s and the 1990s, numerous committees were formed and several experts spoke both for and against the dam. The case went before the Supreme Court which passed a 2:1 verdict in September 2003. The dissenting judgement ordered further studies to establish the safety of the dam.

The main opposition to the dam was on account of it being built in a highly seismic zone. Another factor against it was the geological fragility of the young Himalayan range. So even if the main dam structure was strong, the surrounding mountains were not. Therefore, in the event of an earthquake or due to creation of a big reservoir, a major disaster could occur. Experts pointed out that in the event of the dam being breached, the reservoir built at such a height will be emptied in 22 minutes: within 63 minutes, Rishikesh will be under 260 meters of water. Soon after, Haridwar will be totally submerged. Bijnor, Meerut, Hapur and Bulandshahar will be under water within 12 hours.

On weak ground
The Tehri dam is located in one of the world's most active earthquake zones. Less than 15 kilometres below the dam site lies a fault, the geological boundary between the Indian and the Eurasian continental plates, that is capable of unleashing catastrophic earthquakes. Many seismologists have raised concerns about the structure of the Tehri dam being breached in the event of a major quake. The local protests in the late 1970s focussed on this aspect of the dam. In February 1980, an Environmental Appraisal Committee appointed by the Union government refused environmental clearance to the dam. "Taking into consideration the geological and social impacts accompanying the project, the cost and benefits expected, and after a careful examination of the information and data available, the Committee has come to the unanimous conclusion that the Tehri project, as proposed, should not be taken up as it does not merit environmental clearance," the committee concluded.

In the face of protests, on March 18, 1980, the then Prime Minister Indira Gandhi wrote a note to the Department of Science and Technology to review the project. "It seems that larger areas of very fertile land are being submerged without any commensurate gains. It is true that these decisions have been taken over a period of time but there is great local distress and a feeling that the contractors and other such groups will be the main gainers," she wrote. However, the work on the dam continued, albeit a bit slowly. By 1986, the diversion tunnels had started operating. The voices against the dam also continued rising with more experts coming out in the open against the deficiencies in the dam.

In 1986, a government appointed expert group, headed by Sunil Roy, rejected the dam project. But nobody paid any attention. The Tehri Hydro Development Corporation (THDC) was formed in 1988 to oversee the project. Again, in 1989, the D R Bhumbla committee of the Union ministry of environment and forests reviewed the project. After considering various aspects such as siltation, seismicity and dam safety, it rejected the project in 1990. The project authorities told the committee members that the dam structure was designed to withstand an earthquake of magnitude 7 on the Richter scale. The committee however concluded that this was not adequate as an earthquake of 8.5 magnitude was very much likely in that region.

Dissenting note
A committee of secretaries referred the Bhumbla committee report to yet another expert group. The new expert group included representatives from the University of Roorkee, the Central Water Commission, the National Geophysical Research Institute (NGRI) and V K Gaur, an eminent seismologist and former director of NGRI. Gaur had raised concerns about the design parameters of the dam in 1986 and said that an earthquake more severe than the structure had been designed for could occur at the site. This committee accepted the recommendations made by the earlier committee, that an earthquake of 8.5 was more likely. Surprisingly, it did not make any revisions in the structure of the dam. Gaur was forced to give a dissenting note.

Later, Gaur wrote to P V Narasimha Rao, the then Prime Minister: "The dynamic response of the dam to a real earthquake accelerogram was tested without appropriately scaling the duration of strong ground shaking to about 30 seconds, which would be more representative of the Tehri situation. The test clearly showed that the deformation of the dam continued to increase right uptil 12 seconds when the test was terminated, and would have perhaps maintained this trend for longer if the test had been allowed to run for the full 30 seconds. It is, therefore, difficult to imagine as to how the dam structure would have suffered continued strong shaking for a further duration of 18 seconds. Thus, it can be seen how the conclusions offered by the consultants, by the very deficiency of critical discussion of these assumptions and shortcomings have misleadingly assumed the status of a scientific truth."

Huge protests from the local people forced the government to set up yet another committee to look into the safety aspect of the Tehri dam in 1996. This committee was headed by Gaur. This group, in 1998, recommended that the government should conduct further studies -- a 3-D non-linear analysis of the dam and also a simulated dam-break analysis -- to ensure that in the event of flash floods, the damaging impact was minimal. The Gaur committee, therefore, did not clear the current design of the dam but wanted more analysis to ensure safety.

Instead of implementing the recommendations, the government referred them to the National Committee on Seismic Design Parameters (NCSDP), which comprises of the Survey of India, GSI, NGRI, seismology directorate of the Indian Meteorological Department (IMD) and the Department of Earthquake Engineering of University of Roorkee.

While the Survey of India, GSI and the NGRI failed to offer any comments, the IMD agreed that a 3-D non-linear analysis of Tehri dam should be conducted to gauge its performance against the maximum credible earthquake and also to prepare a simulated dam-break analysis to minimise the damage due to a dam burst scenario. The only dissenter against the Gaur committee's recommendations was the University of Roorkee which thought that carrying out both the recommendations was unnecessary.

The government decided to stick with the dissenting verdict of the University of Roorkee and thus the recommendations of the Gaur committee were never carried out. It was widely reported at that time that the University of Roorkee's interest in the project stemmed out of its major role as consultants to THDC, and therefore, its view was partisan. Finally a committee was set up by the National Democratic Alliance government. The commitee was headed by the then union science and technology minister, Murli Manohar Joshi. The terms of Joshi committee went beyond examining the safety aspects as the members were asked to confer on the damage to the self-purification qualities of the Ganga if the dam was allowed to impede its flow. But even this committee gave a go-ahead to the dam.

In the meantime, the matter was also pending in the apex court on a petition filed, in 1992, by the environmentalist N D Jayal. The majority view of the judgement, in September 2003, contended that the government had put into place all the necessary conditions and safeguards for the project. However, the judges directed that the project authorities should ensure that all the rehabilitation is completed before the closure of the diversion tunnels and consequent filling up of the reservoir. The dissenting judgement reinforced the Gaur committee recommendations to assess dam safety.

What about life span?
The dam authorities and successive governments have repeatedly said that the life span of the dam would be 100 years. But many disagree. "Siltation will take place much faster than expected. Life of the dam will be only around 30-40 years, not 100 years, as claimed by the THDC," says K S Valdiya, former director of the Wadia Institute of Himalayan Geology and a member of the M M Joshi committee. "The ghost may not be there but the fear of the ghost makes your life miserable," Valdiya sums up, referring to the earthquake and the possibility of dam collapse.

In the meanwhile, the anti-dam movement spearheaded by Sunder Lal Bahuguna fizzled out. Rehabilitation issues were somehow lost in all the noise against the project itself. And the protracted construction period meant that rehabilitation could never be carried out satisfactorily.

Lots of stories relating to messy rehabilitation float around Tehri and the surrounding villages. There are examples of people who have taken compensation multiple times, people who were not entitled and still got hefty compensation coupled with houses and shops in New Tehri. Endless tales of corruption do the rounds. But at the other end are those genuine claimants who did not get anything and are still running from pillar to post. The situation is worse in the villages. For them it is not just relocation but an entirely new socio-cultural environment.

People of Malidewal, the first large village that will be submerged, have sown rice again this year. They say that they have nowhere to go and will prefer to drown here. The dam is almost complete and within a few months the final tunnel may be closed and the filling of the reservoir behind the Tehri dam will begin.

Subscribe to Weekly Newsletter :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.