The silt building up in the reservoir cannot be ignored for any decision on the dispute.
In recent years, the controversy over the Mullaperiyar dam has acquired new dimensions. A purely technical matter has turned into an emotional and political issue between Kerala and Tamil Nadu. The entire fight is centred on whether the water level in the Mullaperiyar reservoir should be raised by two meters as demanded by Tamil Nadu, to cater to the needs of additional water for irrigation and power. Kerala opposes this on the ground that the additional water would increase the load on the 116-year-old dam, possibly resulting in a break in the dam, and a disastrous flooding of thickly populated downstream areas in Kerala. Further, the Kerala government fears damage to the dam from seismic tremors. The issue is now being examined by an “empowered committee” of the Supreme Court.
For the best decision, the Mullaperiyar issue needs to be considered from all technical and engineering aspects. It is surprising, therefore, that the silting of the reservoir has not been taken into consideration by any party. Rather, it has been totally neglected. In any dam, silting is a natural hydrological and sedimentological process by which sediments flowing from the upstream catchment area in the river water get deposited in the reservoir.
The process of sedimentation reduces the life of a reservoir. The estimated life of any reservoir is of the order of 120 to 180 years (broadly speaking, not more than couple of centuries). This is the reality. At present most of the Himalayan dams are heavily silted. According to available silt figures, the famous Bhakra dam has lost about 50 per cent of its storing capacity. The Jaldhaka Dam near Siliguri, West Bengal, in the Himalayan range is almost completely silted.
As per available records, the storing capacity of Mullaperiyar Dam has been lost by about 50 per cent during the last 116 years. The rate of silting in peninsular India is less compared to the alluvial rivers of Himalayan region. It may take another 150 to 200 years for the Mullaperiyar dam to get fully silted up — certainly the dam will not last 999 years. Some people argue that some old historical “dams” have stood for the last 1800 years and if these could survive for such a long time, why not the Mullaperiyar dam. But the observation is not based on a scientific understanding of water storage systems.
These ancient “dams” are in reality anicut, or weirs, with a height of about not more than three metres or so. In the engineering lexicon, these are not known as dams. When they overflow during heavy rains, weirs do not get damaged. Further, there is not much silt accumulation in weirs. In an engineered dam, when water flows over the top of the dam, it collapses. With the passage of time, due to siltation, the storing capacity of Mullaperiyar reservoir is bound to decrease steadily, and the availability of water will consequentially continue to decrease. Even if the request of one party to increase the water level is partially or fully granted, it cannot be a final or permanent solution. With the addition of silt every rainy season, the volume of water in the dam would continue to reduce and the demand to raise the water level would crop up again.
Dynamic process
It needs to be realised that the silting of a reservoir is a dynamic process that cannot be stopped or terminated. The silting puts a finite time limit on the life of a reservoir, a fact that, at present, the parties involved may find difficult to accept. The best way to overcome the present impasse is to keep a watch on the silting of the reservoir. When it is silted up to 75 per cent of storing capacity, it would be time to put emotions and political differences aside and start preparing to create an alternate source for water. This, of course, is not an engineering rule, but just a suggestion in the present case. The cumulative accumulation of silt in the reservoir is not dangerous to the stability of the dam as it does not exert any dynamic pressure on the body of the dam. The only danger of silt deposition is effective reduction in the storage capacity of the reservoir.
De-silting of dams has been projected as a solution to sedimentation, and has been tried in some recently constructed dams. Aswan Dam in Egypt was President Nasser's development dream. The Nile is famous for carrying heavy sediments and the dam is heavily silted up. Some experiments were tried to stir the accumulated silt and flush it through an outlet at the bottom of the dam, provided in the design. But the experiment did not produce the desired or expected results. In the case of Mullaperiyar dam such an experiment is not even possible due to its design, type of construction, age of the dam and the building material.
It is hoped that the point of silting in the Mullaperiyar reservoir would be considered by all the parties involved. This would involve studying and making a proper estimation of the accumulated silt, the rate of silting in the foreseeable future, perhaps over a time span of 50 years, and a realistic estimation of the future life of reservoir on account of the siltation. If any decision is taken ignoring the silting of the reservoir, that decision is certainly not going to solve the Mullaperiyar problem.
(The author is a research seismologist: arun_bapat@vsnl.com)
Keywords: Mullaperiyar dam, water rights
The issue of Silt is not going to be problem coz this is not a storage
dam but a diversion dam. In Mullaiperiyar the water level must be more
than 106feet for it to reach the diversion tunnel. The 106 feet water
is death storage not used by any party. So if silt accumulates in the
water bed and reduces the capacity of the dam the water level will
reach the desired level quick and also silt will strengthen the base
of the dam. So silt is good. At present TN is using only 136-106 30ft
of stored and diverted water. Its struggling to get it to 142 feet
storage and divert another 6feet which Kerala is objecting and infact
now its objecting the whole dam itself. I don't see any relevance to
the article with the real issue.
Reacting to the statement "Scientifically and socially the the dam is in good health and capacity to serve the people".
Scientific tests are still going on. The results of the tests are not yet published. Videos of underwater recordings are with the EC and results of analysis is not published. Pending all the results of scientific tests, how one can make a blind statement that the dam is scientifically safe. What is the meaning of a dam being socially safe ?
You claim to be doctor. Please keep your comments to the level of an educated doctor. When one party invites the second party for mutual negotiations and if the second party refuses to come to the negotiating table, who is having ego. Please state your expert opinion.
Safety is the primary concern, but that is not the only concern.There is long standing issue of water sharing/electricity/ etc.Any solution must address all these genuine concerns of the real owner of the dam. No other solution should be accepted.
The author suggestions and explanations are very excellent and true one. The controversy over the Mullaperiyar dam and water distribution is purely political. Water, air and food is for all without any reservation of cast, religion and region. The hidden problem is the ego of man. Nature itself would solve this problem when time will come if man doen't solve.
For the sustainable development of the society this problem should be solved immediately. The matter which is in the court never solved. The Dam/Dam water is not in the court but human ego. It can be solved by the people sitting both the side of Kerala and Tamilnadu without ego. People always blame the politicians. But they are also human. So we have tried to make run away the ego and it will go from high level to low level just like the water flow from high level of dam to low level region. Scientifically and socially the the dam is in good health and capacity to serve the people as evience by above saying.
It is the right time for Tamilnadu to retrieve and desilt thousands of water sourses of Ponds, tanks, anicuts which are found only in revenue and PWD records. Infact most of them were gone to the selfish Political mafias and have become Nagars (Residential areas) named after the ruling party leaders or the parents of them. A welfare state needs Courage to retrieve them from the clutches of the occupants giving them alternate sites for their folly. No where we can see like Tamilnadu that the water sources are dwindling and the administration is not worried about that. At this juncture will it be prudent to fight with the neighbours targetting on political considerations? Ofcourse it would be reparian rights that existed for time immemorial but we should develop the sources without depending only on the neighbours. Store the water that is wasted during the rainy seasons for which the restoration of water sources on records is highly necessary. Will this welfare state act judiciously?
The agreement between the Madras Presidency and the Maharaja of the State of Travancore was devised when the two parties enjoyed unequal power and status. It is unsustainable in an independent India where all the States are co-equal. The argument that we've used the waters for 100 years and we'll continue to use it to eternity is unreasonable.
Tamil Nadu should take steps to gradually eliminate their dependence on Kerala rivers - and more efficiently use its own water resources. Not immediately, but over a sufficiently long period of time, say 50 years.
The water is diverted from periyar dam to tamil nadu and it can be done
only if the water level reaches a minimum of 106 feet,so Silting is more
of an advantage to water diversion process rather than a deterrent.
Majority of catchment areas of Mullaperiyar is uninhabited forest land and the general principles regarding sedimentation and silt accumulation is not valid in the case of Mullaperiyar. Silt becomes a threat to the capacity of the dam when sand and mud from agricultural lands flows into the dam. Politicians have made Mullaperiyar a sentimental issue to exploit the feelings of people on both sides. Mullaperiyar issue is an issue to be resolved by technical people. Proven technologies and tools are available to assess the strength and life of the dam. If the dam is found to be weak, we need to seek technical solutions to resolve the issue. If we examine closely, the politicians are entirely responsible for the loss of property of people in this issue. Unfortunately politicians become rich by making use of Tax payers money and the tax payer has no option to sue the politicians to recover their money from them.
@ Mohideen: hope u are a tamil and thats why such a narrow minded
thought... when will u people learn??? All these while u people were
objecting for KKNP (that includes the CM), u dint even listen to APJ,
now the CM says its for good and i can see many people taking her
side... i still cant think about the regional parties playing a major
role in 2014 and if that happens every state will want to be separate
nation... god alone save the country!!!
Not much has been clarified about "SILT"itself.Is it a type of rich topsoil material&if so has any civil engineering academics reserched on dredging it for both benefitting the farmers as an organic compost while simultaneously enlarging &or recuperating the storage capacity of the dam postponing the political dispute between the neighboring states&hope for saner minds taking over the issue&create a "win-win" situation.
The writer has brouhht up good points on silting but has ignored the disaster opint on silting. He has indicated that the lake upstream of the dam has silted to a depth of 106 ft. and that the solid weight of thsilt will stabilise th dam. But consider this, there is an earth quake that is 6 and above on the RS in the middle of the lake or at the opposite end from the dam. The violent turbalance created would emulsfy the silt into fluid and instead of of 0.99 sg , it would be a fluid at say 1.2/1.3sg slamming int the wall of the dam. There is no more 106 ft. of silt stabalising dam. The soil at the base would be weak and could surely give way.
Look at what happened in Japan. Even though the epicentre was in the sea, where the waves could radiate 360degrees look at the force the wave that hit the coast. Think what happens to an enclosed body of water.
I live in Vancouver and I wonder when the big one will hit us. Do not underestimate the force of nature.
I think, instead of touching the current dam.. any one of the state should construct new one for better alternative.
the politicians shud read this article and they shud make their stands. this article is really worth to read !!!!
Is Arun Bapat a Malayali?
I dont understand what the Author wants to say regarding the silting of the dam. As the silting increases the stability of the dam improves and the stored water quatity is reduced. By raising the level, water storage capacity can be increased to cater to the needs of irrigation and power.The author says that " The only danger of silt deposition is effective reduction in the storage capacity of the reservoir". What is danger in that - only we realise reduced capacity with the advantage of increased stability and Kerala need not have to wory about the impounding danger of dam breakdown and killing of so called millions of lives along the river bank.
Again the Author is trying to bring the wedge between the two states and instigate Kerala again to against this Dam by creating confusion in the minds of the people.If the Author claim is right, then let the Dam reach the natural death by silt in the next 150-200 years by then we are not sure this earth would survive that long.
It is good that you brought this silting issue into the picture.
Nice article mainly people of kerala and Tamils have historical relationship but Bcoz of chandy all spoiled Now its never going to be same for sure....
Nice and quite knowledgeable article !
A very nice unbiased article on mullaperiyar. A fitting reply to ignorant and cunning politicians who have been comparing 13 feet high kallani dam to 170 feet high mullaperiyar dam.
The matter should be resolved peacefully and democratically between two states.
The explanation given by the seismologist throws new light on the whole question. It deserves attention by the powers that be and action taken thereon.Is not the empowered committee of the Supreme Court aware or made aware of of this aspect? Secondly the matter has been taken over by frenzied politicians on both sides for whom this is one more stick to beat the drums with and make political hay while the sun shines. In any event, the problem is very criticsl to the Keralites who live downstream and for them the sword of Damocles is .hanging over their heads. that is the crux of the problem and deserves notice.
The entire fight is not about increasing the water level from +136 feet to +142 feet. Kerala's stand is that the old dam is to be demolished since the dam may get burst in the event of a sufficiently strong earth quake in the region and catastrophe would befall to the people downstream. After construction of the dam, water level was maintained up to +150 feet till about 1980. After the dispute went to Supreme Court, and after due process, the court ordered that the water level shall be maintained up to +136 feet till some strengthening works were carried out and thereafter up to +142. Though major strengthening works were carried out, Kerala did not agree to increase the level and the dispute remains.
Arun Bapat is a seimologist. I have high regards for him. MullaPeriyar dam is unique. The bottom 106 feet is dead storage. I can not understand how water flow to Tamilnadu is going to be affected whether dead storage is water or silt unless the level of silt exceeds 106 feet. In fact more silt means less pressure on the gravity dam.
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