1. ARGUMENT: 37 dams exits in India, which are more than 100 years old and still in service and hence it is not prudent to conclude that Mullaperiyar is unsafe based only citing the age of the structure.
COUNTER ARGUMENT: It is true that there are more than 37 dams exists in India which are more than 100 years old (Source: National Register of Large Dams, 2002). But a close look into the above data shows that out of the above 37 dams, 30 dams are of earthen dams having around 20 m height and more over having only an average gross storage capacity of less than 1 TMC! Hence these earthen dams are only can be qualified to be as ‘earthen bunds’ and does not pose much threat.
If we consider the remaining seven masonry gravity dams, the Mullaperiyar dam surpasses all others with its height of 53.64m and its huge storage capacity of 15.66 TMC. The second one on the above list, Khadakwasla dam, which had already overtopped in 1961 due to the failure of the Panchet dam in the upstream (Maharastra - Pune District). The third one on the list is having a height of only 16.77m. Hence such comparisons have no meaning.
Mullaperiyar dam is a composite gravity dam which lost of much of its strength due to continuous leaching of lime from its core. This dam is situated in an active fault zone, which makes the dam vulnerable to failure in an earthquake of moderate intensity with an epicenter close to the dam. Also the high hazard this dam poses a direct threat to the lives and property of 35 lakhs people living downstream and also a threat to the mega storage Idukki reservoir. Hence Mullaperiyar dam has no parallels and considering its age, deterioration and high hazard nature, must be decommissioned and a new dam must be built.
2. ARGUMENT: No masonry gravity dam has failed so far and hence the fear of Kerala about Mullaperiyar dam is not based on facts.
COUNTER ARGUMENT: This is not true and against the facts. World over Masonry gravity dams have failed and a few examples are shown below.
Year of Failure
Height in m
A doctoral thesis paper from University of New South Wales, Australia ‘An analysis of Concrete and Masonry Dam Failures’ based on a database called ‘CONGDATA’ is put the figure of the total masonry dam failure reported world over as 21. (This research was funded by the dams community in Australia as part of Dam Risk Project, together with ARC and the Faculty of Engineering at the University of New South Wales)
- It reveals that the peaks in failures of masonry gravity dams are noted in dams commissioned in the 1870’s to 1890’s and 1910’s to 1920’s.
- It also reveals that dams within the height range of 15 m to 50 m range are failed more than others.
The above findings are relevant as far as the century old Mullaperiyar Dam concerned because it matches both criteria and the probability of failure of this dam is more compared with others.
3. ARGUMENT: Idukki is having a gross storage capacity of 70.5 TMC at FRL and it is not filled up to its full capacity. Hence Idukki can very well contain, even if worst happens to Mullaperiyar Reservoir!
COUNTER ARGUMENT: It is regretted to note that Tamil Nadu ignore the fact that once the Mullaperiyar fails, the water will traverse through river for a length of 36 kms before reaching to Idukki reservoir. There lives around 75,000 people on the banks of River Periyar in towns like Vallakadavu, Vandiperiyar, Upputhara, etc. Any dam break of Mullaperiyar will completely wash away the entire population between Mullaperiyar and Idukki and hence the Government of Kerala is not prepared for taking any risk in this regard. If we consider this fact, Mullaperiyar dam qualifies to classify as a High Hazard dam as per CWC norms, which means failure will cause loss of life of more than a few people and excessive economic loss (CWC Guidelines for Inspection of Dams, 1987).
More than 6 years during last 30 years (means a probability of occurrence of around once in 5 years!) the Mullaperiyar and Idukki storages together crossed the gross storage of Idukki reservoir. Hence it is evident that if Mullaperiyar dam failed at that time, Idukki dams would have been got overtopped due to the combined storage crossing 70.5 TMC, which Idukki reservoir cannot accommodate in now way. Hence the argument that if worst happens, Mulllaperiyar flows will be contained by Idukki have no relevance. It is important to look at the probability of becoming both these reservoirs filling, it is once in five years, such a high probability! I am shivered to imagine about such a catastrophe of overtopping of dams of Idukki reservoir, which is having a gross storage capacity of 70.5 TMC and having a downstream population of around 35 lakhs people! Is India, which poses itself as super power can accommodate such a catastrophe? It is high time for Government of India to open their eyes and look into the facts which are already available with them, yes, both Idukki and Mullaperiyar reservoir statistics are available with them.
GROSS STORAGE IN TMC
IDUKKI + MULLAPERIYAR
Note:- The gross storage at FRL of Idukki is 70.5 TMC and at MWL is 74.4 TMC
4. Argument: Due to the non-restoration of water level from 136ft to 142ft, Mullaperiyar spills and water is wasted.
COUNTER ARGUMENT: Even though the FRL of the reservoir is kept at 136 feet, Tamil Nadu never denied by Government of Kerala to draw the entire quantity of water from this reservoir. If we consider the period of 1911-1979 (FRL-152ft), we can see that the Mullaperiyar reservoir spilled at a rate of 18.14 days per year to the downstream. But it can be seen that between 1980-2005 (FRL-136ft), the reservoir is spilled only at a rate of 8.62 days per year! It is to be noted that the reservoir spilled 40 years out of 69 years (1911-1979). But it only spilled in 11 years out of the last 27 years and the rest of the years entire water from this reservoir was drawn by TN. This is because of the high rate of emptying Periyar reservoir (due to the increased tunnel capacity from 1300 cusecs to 2100 cusecs done in late 1959) by transferring waters to TN territory and storing the entire waters (due to development of subsequent reservoirs and 1373 tanks in their territory so that the dependable inflow from Periyar can be easily accommodated). Hence it can be concluded that the lowering of water level has not affected TN’s historical water rights (1911-1979) from Mullaperiyar.
5. ARGUMENT: Due to the non-restoration of FRL from 136 ft to 142 ft, and TN’s irrigation benefits are suffering
COUNTER ARGUMENT: It is important to note that the Mullaperiyar spilled only on occasions wherein TN is unable to draw water from Mullaperiyar either due to avoid spilling in their area during the flood years wherein the North-East Monsoon is so active and flooding their area (Eg: Year 2006) or due to some failure of their conveyance mechanism (Eg: Year 2005). It is another fact that if we consider the spilled years, TN irrigated more area during those years than the other normal years and dry years wherein they have taken the entire water.
We can see that less than 5% of the inflow is only spilled from Mullaperiyar, that too during high flood years. It is important to note that during majority of those years TN’s Vaigai Reservoir also spilled and water was wasted to the sea (1984, 1992, 1993, 1994, 1997, 1998, 2004, 2005 & 2006). During the flood years, it is natural that all medium reservoirs will invariably spill and not even a water scarce State like Tamil Nadu can avoid such phenomenon.
It is important to note that TN has added around 22647 ha (55962 acres) ayacut to the Periyar Vaigai Irrigation Project after 1980, ie, lowering of the FRL with World Bank aid and the ayacut is still expanding. If the water diversion is reduced, what is the meaning of this additional ayacuts?
Another aspect is that such huge additions of ayacut, will create problems during lean years even though there will be water available during flood years. It is not advisable to extent ayacut to enormous proportions while the 75% dependable flow from Periyar catchment is around 20 TMC (hardly sufficient for 1,60,000 acres ayacut, which is 10,000 acres more than what British Engineers envisaged) and during lean years the flow dwindles to 15 TMC to 12 TMC. That means lean years the flow wont be sufficient to irrigate even 50% of the ayacut and it naturally result in a blame game. Hence it can be concluded that not because of the lowering of the FRL, but because of the unscientific ayacut development to exploit the water only available during flood years is the real problem of TN and it is not fair to blame Kerala for that. It is a fact that more ayacut developed than the dependable flow only creates more unhappy ryots in lean years and sometimes normal years! The World Bank Report on ‘India’s Water Economy’ narrates this apathy in Periyar-Vaigai basin as an example for the future Indian irrigation planners.
6. ARGUMENT: Spilling of Mullaperiyar to Kerala means wastage of water to the sea!
COUNTER ARGUMENT: This is also a wrong argument without understanding the reality. The spill water from Mullaperiyar is being collected at Idukki reservoir and owing to its huge capacity, Idukki can regulate these waters in a better manner and the waters are sufficient water can be discharged during lean summer months to meet the irrigation demands in Muvattupuzha Valley Irrigation Project. Moreover, these waters can cater the drinking water requirements, saline intrusion problems especially in summer months. It is important to note that during 1886 to 2006, the population of Kerala has increased by six times and the water demand also swelled to around 20 to 25 times. Hence it is a wrong perception that the waters are being wasted into the sea. Also, it is proved that flooding is always helps to recharge the ground water availability to a great extent. It is important to note that while Vaigai is rich in ground water availability, Periyar is not like that and the basin has to depend on its surface waters, which are now being limited to 80 to 90 days of rainy days. Hence the spill water received to the largest storage reservoir is useful to the huge population for various needs. It is important to note that inbasin needs are may get more priority than trans basin needs.
7. ARGUMENT: Even though the water level in Mullaperiyar reached close to 140 feet during spill years nothing happened to the dam. Similarly the recent earthquakes have no effect on the safety of the dam. Hence Kerala’s concerns about the safety of dam are not genuine.
COUNTER ARGUMENT: It is true that the dam sustained the increased water levels around 140 feet. Similarly the dam sustained the earthquakes recorded. But it is important to note that no earthquake of moderate intensity has so far happened close to the active fault below the Mullaperiyar dam. The worst scenario, we are trying to avoid is an deteriorated dam with 142 feet of water and an earthquake of intensity 6 to 6.5 in the fault zone below the dam same time. The good luck that not the dam has yet been seriously tested in a severe earthquake with the above water load and hence the dam is still there. Disaster prevention is more seriously taken by the societies world over in the recent years. Government of India after the Tsunami, Bhuj and Latur earthquakes and Mumbai floods also geared up to meet the challengee of disasters and recognized that the prevention is better than cure. Hence I can quote Koffi Annan, “Building culture of prevention is not easy. While the cost of prevention had to be paid in the present, its benefits lie in the distant future. More over, the benefits are not tangible; they are disasters that did not happen.”
Hence it is prudent that we must show the character of statesman and show the positive attitude to build a new dam instead of waiting for a disaster! This old dam, has the potential to kill millions, of people, is no more unbreakable than the Titanic was unsinkable.