Wednesday, November 30, 2011

Some scientific facts about Mullaperiyar

The earthquakes of magnitude 4.5 at Nedumkandam(1988), 4.3 at Wadakkanchery (1994) and the earthquake of magnitudes 5 that occurred in Periyar basin (12-12- 2000) and 24 tremors of 2010 clearly justify the views of seismologists that the seismic activity has recently. The study by IIT Roorkee confirms this. In USA the geological survey uses aircraft with magneto-meters for studying the magnetic anomalies and detect the hidden faults to assess the seismic hazard potential in the selected zones. The continuing work of the dedicated and intelligent earth scientists is helping to protect the lives and properties of citizens in different regions from the earthquakes that are inevitable in the near future. But unfortunately the Indian experts without undertaking such investigations on seismic potential of Mulla Periyar dam are jumping to make unscientific pronouncements on the safety of the dam although such expert opinions are likely to present risks to the life of lakhs of people in Kerala.

The probability of failure of a dam depends on factors like seismicity of the area, spillway capacity, nature of foundations, seismic design quality of construction, feasibility of disaster management, bombing by terrorists or enemy countries. About 10% of the dams failed in India and abroad and about 2% of them are reported to have collapsed. The Vaiont dam in Italy failed in 1963 due to the collapse of the mountain slopes around the reservoir basin due to a series of medium earthquakes. Some dams in the western ghats of Maharashtra and Karnataka have also collapsed. About 2000 dams have been identified by the US experts as unsafe and it is estimated to cost $1000 million to rehabilitate them. Under the dam Safety Acts in USA and Canada, the risk analyses and dam-break scenarios are used as tools to assess the hazard potential of a dam as it provides firstly the data required for scientific estimation of spill way capacity and secondly to predict the flood wave depth and flood wave arrival times for identifying the villages and towns that could be drowned by the flash floods due to the collapse of the dam. Thus flood management in preventive terms means dam safety and in protective terms flood plains management. According to the International Standards (ICOLD –57, Bulletin46) seismic safety of the dam ensures that firstly the dam does not suffer significant damage due to an anticipated earthquake and secondly the damage to the dam is limited and no catastrophic failure occurs leading to uncontrolled release of water due to a maximum credible earthquake.

While studying the Environmental safety of Mulaperiyar dam, two expert committees, one appointed by the Kerala state and another by the union Government presented contradictory recommendations on safety aspects of the dam. A perusal of Newspaper reports on the findings of Expert Committee of the Central Government indicates that the report gives a false impression about the safety of Mulaperiyar dam and naturally the farmers of Tamil Nadu have become suspicious about the genuine grave concerns of Kerala .Safety and Environmental hazards of Mulaperiyar and other dams like Iddukki are questions of life and death to Kerala and such issues are too serious to be blindly left in the hands of Experts since they involve not only the technical but also the major social problems. It is necessary to create proper awareness on this controversial problem so that the people can safeguard their right to life and the environment as envisaged under section 51(A) of the constitution of India.
The experts group of Central Water commission according to Mr.K.Paramesaran Nair alone representative of Kerala Government had floughted the fundamental rules of dam safety. Mr.Nair says that 95% of the water from the Mulaperiyar reservoir is now given to Tamil Nadu which wants the balance of 5% which amounts to 1.2TMC and for this purpose Tamil Nadu demands to raise the height of the dam from the present level of 136ft to 152ft. or even 145ft. and this demand poses threat to the public interests of Kerala. If the height of dam is increased and if an accident occurs to the dam the flash floods will destroy Kumili town and millions of people will perish in four districts downstream of the dam in Kerala state. Besides 10,000 acres of forest land would be submerged and 10,000 tribal families will be deprived of their food and shelter. In addition the region is biodiversity hot spot. This poses a serious threat to the ecosystem and ecological balance. The claim of Tamil Nadu that the dam has enough strength to hold more water is not based on scientific grounds.

The annual leaching from the dam is 30 tons of water per year and cement grouting was done. The Probable Maximum Flood (PMF) used in the design of Mulaperiyar dam was 2495 cumecs and it was revised to 6000 cumecs as suggested by Central Water Commission. Idukki has a PMF of 8000 cumecs and Idukki would not be able to handle a major inflow of 6000 cumecs, if Idukki itself has water upto FRL or near to it. If both the projects are subject to flooding at the same time is pose a threat to the dams that means even if Mulaperiyar does not fail. Since several small rivers while diverted into Idukki subsequent to its completion. The failure of Mulaperiyar dam could be catastrophic for Idukki project. Idukki dam that was built to hold 2000million cubic meters of water (70 TMC) will have to absorb flash floods of 443 million cubic meters (15 TMC) from 50 kms away and if it fails hundreds of towns and villages of Periyar basin in Kerala will be wiped out if the dams of Idukki failed. Idukki was designed for PGAh of 0.05g and PGAv of 0.025g. It means that the dams cannot withstand earthquakes of higher intensity expected in the area in the near future. Lower Periyar dam downstream is designed for PGAh of 0.1g. However landslides in the catchment due to recurring earthquake tremors and intense rains can cause failure of the dams as had happened in the case of Vaiont dam in Italy in 1963. The scientific studies indicating unstable hill slopes and heavy siltation of the reservoirs indicate the hazards waiting in the wings.

Medium earthquakes like the once that occurred in Periyar basin have produced very high Peak Ground Acceleration (PGA) in several Geo-tectonic environs. For instance the Ancona earthquake of 4.6 magnitude in Italy (1972) produced PGA of 0.61 and the Oroville quake in USA (1975) of magnitude 4.6 produced PGA of 0.63 and the Salvador earthquake (1986) of 5.4 magnitude produced a PGA of 0.70 and the Cerro earthquake of USA (1987) of magnitude 5.5 produced a PGA (horizontal) of 1.12g and a vertical PGA of 0.61 and hence the Mulaperiyar dam which was not designed to withstand any earthquake can never be expected to be safe particularly when it is century-old and located in a highly earthquake prone zone.

If the design, construction, operation and maintenance of the project works placed in the hands of Tamil Nadu and the beneficiaries are Tamil farmers of Madurai and the potential victims of the catastrophic failure of the dam are in hundreds of villages and towns of Kerala, it is impossible to preface the risk analysis and Disaster management reports for emergency evacuation of people likely to be killed due to a maximum credible accident to one or more dams on Periyar river. In the absence of these basic reports, the recommendations of the Expert committees appointed by the Central Government to study safety aspects of Mulaperiyar dam become null and void.

Failure of dam also occur due to the following causes:
1.Liquefaction of the materials used in the dam.
2.Liquefaction in the foundation soil
3.Wrong estimation of the peak ground acceleration due to wrong assumptions on seismic potential of the area in terms of magnitude, intensity and methods followed for estimating effective Peak Ground Acceleration
4.Prediction of deformations and stresses from earthquake loading
5.Inability to make necessary modifications in the size of the dam that will provide an acceptable response in case the predicted deformations or stresses are intolerable due to revised increases in seismicity of the area during project construction.
6.Inability to estimate performance of the dam and foundation characteristics by comparison with case histories of dam failures
Other modes of dam failures include:
7.Slope failures induced by ground motions
8.Sliding of the dam on weak foundation materials
9.Disruption of dam by major fault movement in the foundation
10.Loss of freeboard due o differential tectonic movements
11.Loss of freeboard due to slope failures or soil compaction
12.Piping failure through cracks induced by the ground motions
13.Overtopping of dam due to seiche in the reservoir
14.Overtopping of dam due to slides into the reservoir
15.Overtopping of dam due to failure of spillway or failure of dams upstream.

The water level in Periyar was reduced from 152ft. to 136ft. in 1979 due to doubts raised about the strength of the Century-old structure. When American experts are reviewing the safety of all their dams in the light of the latest tremors and are dismantling some old dams, strengthening some weak ones and redesigning some more by reducing their storage levels so that emergency evacuation measures become feasible for implementation during collapses of dams to minimise loss of lives and properties, how can some Indian experts who have no indepth knowledge on seismic safety of dams venture to vouchsafe for the safety of Mulla Periyar dam without making any scientific analysis pertaining to all the above relevant factors as followed in the developed countries in this regard?
The State Government's finding that the Central Water Commission (CWC) underestimated the probable maximum flood (PMF) in Mullaperiyar catchment when it recommended strengthening measures for the dam back in 1979 heightens public concerns about the safety of the dam. (PMF is the flood that can be expected from the most severe combination of critical meteorological and hydrologic conditions that are reasonably possible in a region.) This is something that had not been taken note of by the technical committee of the State when it recommended in the Nineties that the water level in the reservoir should not be allowed beyond 136 feet. Nor had these arguments been presented before the Supreme Court. The key point is that the CWC had recommended a PMF of 6,003 cubic metres per second (cumecs). However, an actual flood in 1943 was of 8,453 cumecs. This means that water will overtop the dam if the maximum possible flood occurs.
Because this is such a crucial safety aspect of the dam, the pattern followed uniformly in all dams in the country is to identify the maximum observed flood that has occurred in the catchment area. Then, this figure is significantly boosted up and the PMF identified from this boosted-up figure.In the case of Mullaperiyar dam, the maximum flood that took place in the reservoir was 8,453 cumecs. However, curiously, for the purpose of determining the PMF, the then Chairman of CWC recommended 7,249 cumecs, a figure lower than this maximum amount. This recommended figure was again lowered for reasons unknown to 6,003 cumecs. Even with this artificially lowered figure, the water will flow over the top of the dam but for the parapets. Not only this but also the siltation in the dam will further contribute to the rising of the mean water level so that water flows over the top of the dam.
While assessing the safety of the dam, the expert committee of the CWC had taken the design horizontal seismic co-efficient as 0.12 g instead of 0.18 g. The value 0.18 g is the least recommended value for zone III as per IS 1893-1984 where Kerala is situated. In this context it may be noted that the standing committee set up by the Union Government for advising the seismic coefficient for the river valley projects recommended a value of 0.24 g. "This extremely low value of 0.12 g has incorrectly made the dam `safe' for water level up to 142 ft. This action of the expert committee is against the guidelines published by the CWC in this regard. It is evident that if the least seismic co-efficient for zone III is taken for stability analysis, Mullaperiyar reservoir is not at all safe even to hold water up to the height of 136 ft."
It can be seen that the Central water Commission who should guide the states on safety of Dams is not discharging its responsibilities in public interest on highly scientific lines. For instance, as per international standards, if the historically recorded peak flood in Mullaperiyar in 1943 was 8,453 cumecs, the PMF should have been taken atleast 1.5 times that value and estimated at about 12,680 cumecs or based on the failure of the Machhu Dams in Gujarat PMF value should have been taken at about 17,000 cumecs . Sardar Sarovar dam and Mulla periyar dams are located in the same seismic Zone-III and hence the same seismic coefficients must be applied to ensure safety of the dam.

Hence the views of kerala state are justified and the central government has the responsibility to protect the lives of people downstream the dam.

References :

Note: Apology to original authors. I am copying your contents without asking permission. I think that the authors will understand the urgency and gravity of situation and pardon me.

Keywords: Mullaperiyar, mullaiperiyar


  1. Kudos bro!! Keep up the spirit

  2. The authorities need to open their eyes and save the people. The people of Kerala need to awake and join hands. Tamilians are really foolish and misled by their dirty politicians

  3. I think that this issue is already dead from media. I guess all those 4 districts will be washed to sea one day without ant notice and rest of the world will understand the seriousness then only. Let us pray for their souls. Wish them all a happy death.

  4. Why the government of India is showing step-mother approach towards kerala?