Mullaperiyar: The real truth about our dam problem

Last Updated: Tue, Dec 13, 2011 04:58 hrs

New Delhi: India has 115 century-old dams in various states of decay and poised to wreak havoc. What’s more, no one seems to be either able or willing to fix the problem.

The panic surrounding the 52 metre (300 feet) Mullaperiyar dam may be an understated response when you consider another - much graver - threat that looms over the country: the plethora of hundred-year old dams, some 115 of them, that are more than a century old and capable of unleashing potential devastation if breached. All of these dams are still very much in use - the oldest being the Thonnur Tank (24.38 metres high), located in Karnataka and dating back to 1000 AD.

We seem to love our dams - or we’re perhaps just apathetic about retiring them. In other countries like the United States, decommissioning them is de-rigeur. In the US, about 1,000 dams were decommissioned in the last two decades alone (out of 75,000 dams that operate in the country), says Himanshu Thakkar, who heads the research and advocacy group South Asia Network that focuses on Dams, Rivers & People. In India, however, there is no such move. According to a study done on the ageing Mullaperiyar dam - which is now in the middle of an acrimonious dispute between Tamil Nadu and Kerala—by IIT Delhi, the dam’s hydraulic tests for safety don’t pass muster.

Mullaperiyar first developed cracks during an earthquake in 1979. When IIT Roorkee recently tested it for the first time in its history for seismic safety, the dam failed the test. Consequently, it was labelled ‘unsafe’ in the event of a high intensity quake. (The area had 22 tremors this year, touching up to 4 on the Richter scale). Kerala has recommended decommissioning the dam and building a new one instead, but neighbour Tamil Nadu has fiercely resisted the move since it may lose favourable privileges to operate the dam that were first given to the state by the British in 1895.

However, the problem of ageing dams doesn’t have everybody worked up into a tizzy. Scientist DK Paul, Professor of Earthquake Engineering at IIT Rourkee, doesn’t seem to be too worked up about old dams, though. “I have not seen any dam decommissioned so far. If the dam can store water then it works. If silt accumulates, then today we have the technology to flush it out. But if the soil starts getting eroded, which is called piping, then it should be decommissioned.’’ Dams, especially concrete ones, are sturdy structures and each dam has a project authority which apparently does periodical safety checks. Paul says seismicity of areas can be a problem but seismic Zone Five which has the most frequent and most powerful tremors is in the Himalayan regions. Besides, he says that most old dams are lower than 30 metres—often between 10 and 20 metres—thus incapable of causing a major deluge. There are some, though, which touch 50 metres, like Mullaperiyar.

The bulk of old dams—thirty of them—are in Maharashtra, a state that is mostly in Zone 4. The oldest one—the Dhamapur, 11 metres high—dates back to 1600 AD. The Tansa dam which is 41 metres is located close to Mumbai and was built in 1892. Rajasthan and Gujarat each have 20 century-old dams, and both are located in zones three and four. Paul has confidence in the safety monitoring mechanism of each dam, but the fact that Mullaperiyar has never had seismic safety looked at questions his faith in the monitoring mechanism that takes place.

Even if you decided to evaluate a dam’s potential to wreak havoc just based on which seismic zone it lies in, you would have overlooked another big reason to worry about dams—namely, Reservoir Induced Seismicity—where a place becomes seismic after a large dam comes up in the area with a heavy load of water, not to mention damage caused by faulty operation of dams. The latter was seen in the floods in Orissa year after year, says Shripad Dharmadhikary who has authored books on large dams.

The Latoor quake, which led to the breach of the then-brand new Koyna dam in Maharashtra in the 1960s as well as the Idukki tremors are all dam-induced as these did not fall in a highly seismic zone, says Dharmadhikary. Kerala is Zone 2, while Maharashtra is in both Zone 3 and 4. Even if the dam is strong and does not breach, the people in the surrounding areas would suffer the impact of quakes caused by the dam, he says. Paul agrees that sometimes dams can lead to seismicity in an area but it is not the general rule. Plus, dam induced quakes are usually small, he says.

All of this would be at least fodder for first debate, and then appropriate action or policy if there were an organisation considered to be credible and effective in monitoring dams and framing rules on dam safety. Activists like Himanshu Thakkar and Dharmadhikary say that the fiasco at Mullaperiyar perfectly highlights this void. The Central Water Commission under the Water Resources Ministry is meant to be that organisation. It monitors the construction and design of each dam and it is equipped with the expertise to do so, says Paul. Yet, the CWC has been unable to weigh in on this issue and in fact, it has little credibility as far as dam safety goes, says Thakkar. The World Bank which did a decade-long dam safety project in four states ending in 2000, said in its project report that CWC was neither proactive in addressing safety issues nor did it question the expertise of its engineers. “While CWC accepts its role as having responsibility for safety issues relating to downstream areas as a result of projects on interstate rivers, it is not playing a proactive role mainly due to the advisory role it is called upon to play on projects/dams constructed on inter-state rivers,” it says in a report. That could lead to disastrous results: In Rajasthan, the hoary Jaswant Sagar dam breached in 2007 creating havoc. It was one of the dams included in the Bank-aided safety project and Thakkar says that it perfectly exposes the failure of the present system.

The World Bank is blunt when it comes to safety aspects of dams. “States generally do not have adequate hydrological capability to estimate design floods and review flood operating strategies,” it states in its project report. “They prefer to rely on CWC or consultants. However, consultants entrusted with probable maximum flood (PMF) analysis have not always performed well. This appears to be due in part to lack of precise terms of reference and adequate supervision. Engineers in India are encouraged to be generalists, and hydrologists are seen as largely within the engineering profession. As disciplines such as hydrology become increasingly technical, this generalisation is becoming outdated.’’

A damning indictment on our record in not just dam safety, but our approach to disaster management in general.

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