Mullaperiyar Dam - A Permanent Threat to Kerala

View of the Mullaperiyar dam and the famous Thekkady lake

Lease Deed of 1886 and Supplemental Agreement

A lease deed was executed in 1886 between the Maharaja of Travancore and the Secretary of the State for India, for irrigation works by the Madras Presidency for diverting all waters of Periyar River of Kerala flowing into the land bounded by a contour line of 155 ft above the deepest point of the bed of the Periyar river to Vaigai basin for a period of 999 years. Two supplemental agreements were executed in 1970 by the successor Governments of Kerala and Tamil Nadu. As per the first supplement agreement, the lease rent was enhanced from Rs.5 per acre to Rs.30 per acre with a provision to revise the same in every 30 years. The second one permitted Tamil Nadu to generate electricity using the waters of Mullaperiyar.

Mullaperiyar Dam

The 155 ft high Mullaperiyar dam is a composite gravity dam built during the period 1887–1895. The front and rear faces of the dam are built with uncoursed rubble masonry in lime surkhi mortar. The hearting, which accounts for 62% of the volume of dam, is constructed of lime surkhi concrete. This dam was constructed at a time when the dam technology was in its infancy and hence does not meet the modern requirements of design and construction. The major deficiencies are the following:

• Earthquake and Uplift forces were not considered in the design of the dam

• No drilling and grouting were done to strengthen the foundation of the dam

• No drainage gallery was provided in the dam body

• Transverse contraction joints were not provided in the dam

Deterioration of the Dam due to continuous leaching of lime

Distress started developing in the form of wetness and seepage on the downstream face of the dam from initial filling onwards. Seepages through the body of the dam increased continuously causing fear in the minds of British engineers. For controlling the seepage, the authorities treated the upstream face of the dam by guniting and the inside dam body by grouting. Guniting was done on the upstream face above 112 feet during the period 1930–1935. Cement grouting work was carried out on two occasions, viz, 1922-1935 and 1961-1965. The total quantity of cement consumed during these two grouting operations was 543 tonnes. Records show that lime leached out from the body of the dam during its life till date is many times more than the above quantity. The leaching has naturally reduced the density of the materials and hence the total weight of the dam.

As can be seen now, in many areas on the upstream face of the dam plastering has peeled off and mortar in the joints of rubble masonry washed away exposing hollow spaces. The condition of the upstream face below 112 ft where no guniting could be carried out due to the continuous presence of water would be much worse than this.

a horizontal crack in the top of the dam

Strengthening carried out during 1980s

In spite of the guniting and grouting operations in 1960s, seepage through the body of the dam continued. The deteriorated condition of the dam alarmed the people living downstream. A deep fear psychosis developed in their minds. Government of Kerala approached Government of India and apprised them of the grave situation.

Government of India sent a team headed by the Chairman, CWC for inspecting and evaluating the safety of the dam, in 1979. Having realised the seriousness of the situation, the team gave directions to lower the Full Reservoir Level (FRL) of the reservoir forthwith to 136 ft. The team also recommended to study the possibility of locating a suitable site downstream of the existing dam for constructing a new dam. The other strengthening measures recommended by them included cable anchoring, RCC capping on the top, enhancing the spillway capacity and providing a concrete backing on the downstream side of the existing dam.

In 1979 itself a joint team of engineers of Kerala and Tamil Nadu located a technically suitable site for a new dam 1300 ft downstream of the present dam where a new dam could be constructed without endangering the safety of the old one. However, for reasons unknown, this proposal was not pursued. Instead Tamil Nadu proceeded with the strengthening measures, may be then intended as a temporary arrangement.

Government of Kerala took a firm and reasonable stand right from 1980 onwards that the FRL of the reservoir should be maintained only at 136 ft even after carrying out the strengthening works as that would not impart the old structure its original strength. This was conveyed to Government of India and Tamil Nadu many a time. But discarding this technically correct stand, the Central Water Commission(CWC) issued a Memorandum on Rehabilitation of Mullaperiyar Dam (1986) in which they recommended the raising of water level to 152 ft after completion of all the strengthening measures advocated.

Litigation in the Hon’ble Supreme Court

In 1997-98, various writ petitions were filed before Kerala and Madras High Courts regarding the issue of water level to be maintained in the Mullaperiyar reservoir. In August 1998, two transfer petitions were filed before the Hon’ble Supreme Court of India citing the possibility of conflicting orders from the two High Courts.

During the hearing of the transfer petitions, Hon’ble Supreme Court desired in its order dated 28th April 2000 that the Minister of Water Resources might convene a meeting of the Chief Ministers of both the States, to amicably resolve the issue. Consequent to this, a meeting was held at New Delhi on 19th may 2000. But due to serious differences on the issue, no consensus could be reached. Finally, the Minister of Water Resources constituted an Expert Committee headed by Dr. B.K. Mittal, Member (D&R), CWC to go into the details of the safety of the dam and advise him on raising of water level in the reservoir.

Unfortunately, the composition of the Expert Committee and the Terms of Reference were fixed without any consultation with the Government of Kerala. Out of the seven members of the Expert Committee, three members were from CWC and two other experts were those having obligations to CWC. As such, it can be reasonably expected that the recommendations of the Committee will be only in line with the earlier stand of the CWC on this issue. This fact is confirmed by the contents of the Expert Committee Report.

The Expert Committee submitted its final report in March 2001 to the Ministry of Water Resources recommending the raising of water level to 142 ft forthwith and to 152 ft after strengthening the baby dam, without giving due consideration to the valid points raised by the member representing Kerala in various Committee meetings.

The Hon’ble Supreme Court of India relied on the Expert Committee Report and delivered its final judgement on 27th February 2006 allowing Tamil Nadu to raise the water level of Mullaperiyar reservoir to 142 ft forthwith.

Amendment Act of 2006

Meanwhile, the Kerala Legislature amended the Kerala Irrigation and Water Conservation Act, 2003 in March 2006. The amended Act listed 22 old dams situated in Kerala including Mullaperiyar dam, which are endangered due to their age, as scheduled dams and freezed their FRL to ensure the safety of the people living downstream.

Tamil Nadu challenged the Amendment Act of 2006 in its application to Mullaperiyar dam by filing an Original Suit before the Supreme Court. The Government of Kerala has already made arrangements to defend the case effectively. However, the concern over the safety of the structure of this old dam remains. Tamil Nadu views it as a purely legal issue. For the Government of Kerala, it is for discharging its basic responsibility of ensuring security to the lives and properties of millions of its people.

PMF and flood routing studies done by CWC

Tamil Nadu had fixed the Probable Maximum Flood (PMF) for Mullaperiyar as 2.12 lakh cusecs, which was endorsed by the Central Water Commission in their Memorandum on Rehabilitation of Mullaperiyar Dam (1986). As the recommended PMF was much lower than the recorded maximum flood of 1943, Kerala requested CWC to supply the workouts of arriving at the above figure to verify its correctness. But the response to the above request was negative.

Subsequently, Kerala managed to get the above details in April 2008 under the RTI Act. The flood routing studies of the CWC revealed that when the PMF impinges the reservoir at 136 ft, the water level would go up to 156.40 ft with one vent inoperative and 156.02 ft with all vents open. Hence, the Mullaperiyar dam would overflow even with the PMF of 2.12 lakh cusecs and as such the dam is hydraulically unsafe. It was quite unfortunate that to circumvent this, it was recommended to increase the height of the parapet wall of this old dam with reinforced concrete construction. This recommendation would increase the water pressure on the dam and increase the threat of failure during flood. Also any rise of water level above 155ft will be contravention of the lease deed of 1886.

PMF studies done by IIT, Delhi

Government of Kerala entrusted Dr. A.K. Gosain of IIT, New Delhi to recommend the value of PMF applicable to Mullaperiyar reservoir and also to carry out flood routing studies. The Institute considered all relevant hydrological aspects and recommended a figure of 2.91 lakh cusecs as PMF instead of 2.12 lakh cusecs endorsed by the CWC. The Flood routing studies carried out revealed that when the PMF impinges the reservoir with water level at 136 ft, the reservoir level would go up to 159.42 ft with one vent inoperative and 158.67 ft with all vents open. Since the water level goes above the MWL of 155 ft and stays there for hours, IIT Delhi has declared that ‘Mullaperiyar dam is hydrologically unsafe’.

Seismic studies conducted by IISc, Bangalore and CESS, Trivandrum

Immediately after the occurrence of the earthquakes in December 2000 and January 2001 in the vicinity of the Mullaperiyar area, the Government of Kerala entrusted a team of scientists and engineers from IISc, Bangalore and CESS, Trivandrum to study the seismic activities in the area and to assess the seismic safety of the old Mullaperiyar dam. They found that the region is susceptible to earthquakes of intensity up to 6.5 in Richter scale. Having studied the structural condition of the old dam in detail, the team recommended that ‘it is not prudent to increase the water level in the Mullaperiyar dam from the existing level of 136 ft, under any circumstances’.

Even though Government of Kerala submitted this report before the Hon’ble Supreme Court of India at that time, they did not consider the above report relying on CWC’s submission that the analysis was done without considering site specific seismic parameters of the region. But it is worth noting that before reaching the conclusion that the dam is safe for earthquake forces, neither the CWC nor the Expert Committee considered the site specific seismic parameters applicable to Mullaperiyar region for finding out the seismic safety of the Mullaperiyar dam.

Site Specific Seismic Study and Dynamic Analysis done by IIT, Roorkee

The Government of Kerala entrusted Dr. D.K. Paul of the Earthquake Engineering Department of IIT, Roorkee to carry out site specific seismic study for Mullaperiyar dam. The study conducted by IIT, Roorkee has concluded that the Maximum Considered Earthquake (MCE) possible in Mullaperiyar region is of magnitude 6.5 in Richter scale and it produces a PGA of 0.21g at the site.

CWC has taken an assumed value of 0.1g and the Expert Committee a value of 0.12g as the seismic parameter of the Mullaperiyar Dam. In the light of the site specific study by the IIT, Roorkee that the seismic parameter applicable to Mullaperiyar dam is 0.21g, the conclusion of CWC and the Expert Committee that Mullaperiyar dam is seismically safe on the basis of assumed lower parameters as above is not at all dependable and is thoroughly misleading.

The Detailed Structural Stability Analysis of IIT Roorkee clearly indicate the following:

• The Main Mullaperiyar Dam even under DBE condition (seismic co-efficient of 0.12g) under reservoir level of 136ft, the value of tensile stresses are found more than double the ultimate apparent seismic tensile stresses. The MCE condition makes the things much worse.
• Even without earthquake forces, the Main Mullaperiyar Dam is unsafe for flood conditions (MWL) since the tensile stresses in the heel of the dam are found to be more than double the permissible apparent tensile stresses.
• In the normal operating conditions, the tensile stresses in the Mullaperiyar Dam at the heel are at the border level of the allowable stresses.

IIT, Roorkee made the following recommendation finally, "Based on the analysis, both Main Mullaperiyar Dam and Baby Dam are likely to undergo damage which may lead to failure under static plus earthquake condition and therefore needs serious attention."

Ageing is an irreversible process

No amount of rejuvenation by any means can perpetuate the 114 year old deteriorated Mullaperiyar dam. Ageing is a nonretrievable process in the case of water retaining structures also, as is the case with living objects. Mullaperiyar dam began to age sending a series of warning signals about its diminishing strength and capacity. There is a limit to the number of years one can keep dams in service through maintenance and strengthening measures. All over the world, citizens, Governments and organizations have begun to review the safety of their dams as per modern standards and design criteria. Hundreds of dams have already been dismantled or decommissioned in an attempt to allay the fears of the people living downstream and to ensure safety to their lives and properties.

All over the world, citizens, Governments and organizations have begun to review the safety of their dams as per modern standards and design criteria and hundreds of dams have already been dismantled in an attempt to allay the fears of the people living downstream and to instill confidence in their minds. Rebuilding of a new dam below the old Victoria dam in Australia in 1981, when the old dam was found unsafe as per modern safety requirements is one of the many examples.

Downstream deteriorated condition of the dam exposed when water level gone to 109 ft. No repairs can be done below this level since there is always water below this since 1895

Economics of Mullaperiyar Waters

Tamil Nadu diverts annually an average of 21 TMC of water from the Mullaperiyar reservoir. Using the above waters, Tamil Nadu is presently irrigating a gross ayacut of 2.5 lakh acres and getting an annual return of around Rs.325 crores. Also, Tamil Nadu is generating electricity from the above waters to the tune of 490 Million Units per annum. Considering a minimum sale price of Rs.4 per unit of electricity, the annual income from power generation is about Rs.196 crores. Thus Tamil Nadu is reaping a total benefit of around Rs.521 crores per year from the Mullaperiyar waters.

Meanwhile, Government of Kerala receives an annual lease rent of Rs.2.58 lakhs per annum for an area of 8692.97 acres leased out to Tamil Nadu. The royalty which Kerala receives from power generation comes to Rs.7.67 lakhs per annum. Thus the total financial benefit to Kerala comes to only Rs. 10.25 lakhs per annum from the loss of Kerala’s own Mullaperiyar waters.

New dam and Continued Supply of Water

The Chairman, CWC as early as in 1979 recommended that the permanent solution to this issue is the construction of a new dam. This proposal was put forward by Government of Kerala during the meetings held at New Delhi chaired by the Union Minister for Water Resources and attended by the Chief Ministers of Kerala and Tamil Nadu. Kerala has also assured Tamil Nadu that the continuous supply of water from Mullaperiyar will be maintained from the new dam for the needy farmers of the friendly neighbouring state in future also. This assurance of continued water release is already conveyed to the Government of India and the Hon’ble Supreme Court of India. But, for reasons unknown, this solution was not yet taken seriously and pursued by Tamil Nadu. So the Cabinet of Kerala State took a decision to construct a new dam, to avert the permanent threat that looms large over its millions of people.

the public agitation for a new dam at Mullaperiyar by the people 

Conclusion

People of Kerala are always known for their magnanimity and good neighbourly attitude. They are keen to ensure continued supply of Mullaperiyar waters to the needy farmers of Tamil Nadu. But they cannot sacrifice their lives and properties while doing this. Mullaperiyar dam has to be there in the years to come if Tamil Nadu needs Mullaperiyar waters for their use. Judging from its present deteriorated condition and the various findings of experts in various specialties, the dam is a high risk structure which can fail at any time causing unimaginable havoc downstream. An old dam which does not satisfy modern technical standards has to be decommissioned well before its ultimate collapse. Visionary leaders and engineers should take timely decisions to dismantle such old risky structures and to replace them with modern constructions. With the goodwill and cooperation of the friendly Tamil Nadu and Government of India, we can hope that the new Mullaperiyar dam will become a reality in the immediate future itself.