Mullaperiyar Dam

 

Mullaperiyar Dam is a masonry gravity dam on the Periyar River.It is located 881 m (2,890 ft) above mean sea level on the Cardamom Hills of the Western Ghats in Thekkady, Idukki District of Kerala, South India. It was constructed between 1887 and 1895 by the British Government to divert water eastwards to Madras Presidency area. It has a height of 53.6 m (176 ft) from the foundation and length of 365.7 m (1,200 ft).^[1] The Periyar National Park in Thekkady is located around the dam's reservoir. The dam and the river are owned by and located in Kerala but the dam is controlled and operated under a period lease by neigboring Tamil Nadu state. The safety of the dam has been a matter of concern and a point of dispute between Kerala and Tamil Nadu States.

Purpose

The Periyar river which flows westward into the Arabian Sea was diverted eastward to flow towards the Bay of Bengal and provide water to the arid rain shadow region of Madurai in Madras Presidency which was in dire need of a greater supply than the small Vaigai River could give.The dam created the Periyar Thekkady reservoir, from which water was diverted eastwards to via a tunnel to augment the small flow of the Vaigai River. The Vaigai was dammed by the Vaigai Dam to provide a source for irrigating large tracts around Madurai. Initially the dam waters were used only for irrigation. Later, the Periyar Power Station in the lower Periyar, Tamil Nadu was built which generates hydro-electricity from the diverted waters.

Design

The Mullaperiyar Dam is a gravity dam made with limestone quicklime). Gravity dams use their weight and the force of gravity to support the reservoir and remain stable. The main dam has a maximum height of 53.6 m (176 ft) and length of 365.7 m (1,200 ft). Its crest is 3.6 m (12 ft) wide while the base has a width of 42.2 m (138 ft). It consists of a main dam, spillway on its left and an auxiliary dam (or "baby dam") to the right. Its reservoir can withhold 443,230,000 m³ (359,332 acre·ft) of water, of which 299,130,000 m³ (242,509 acre·ft) is active (live) storage.

 

Feasability studies

The unique idea of harnessing the westward flowing water of the Periyar river and diverting it to the eastward flowing Vagai river was first explored in 1789 by Pradani Muthirulappa Pillai, a minister of the Ramnad king Muthuramalinga Sethupathy, who gave it up as he found it to be expensive The location of the dam had first been scouted by Captain J. L. Caldwell, Madras Engineers (abbreviated as M.E.) in 1808 to reconnoitre the feasibility of providing water from the Periyar river to Madurai by a tunnel through the mountains. Caldwell discovered that the excavation needed would be in excess of 100 feet in depth and the project was abandoned with the comment in his report as "decidedly chimerical and unworthy of any further regard".

The first attempt at damming the Periyar with an earthen dam in 1850 was given up due to demands for higher wages by the labour citing unhealthy living conditions. The proposal was resubmitted a number of times and in 1862, Captain J. G. Ryves, M.E., carried out a study and submitted proposals in 1867 for another earthwork dam, 62 feet high. The matter was debated by the Madras Government and the matter further delayed by the terrible famine of 1876-77. Finally, in 1882, the construction of the dam was approved and Major John Pennycuick, M.E., placed in charge to prepare a revised project and estimate which was approved in 1884 by his superiors.

Lease

 

On 29 October 1886, a lease indenture for 999 years was made between the Maharaja of Travancore, Visakham Thirunal Rama Varma and the Bitish Secretary of State for India for Periyar Irrigation Works. The lease agreement was signed by Dewan of Travancore V Ram Iyengar and State Secretary of Madras State J C Hannington. This lease was made after 24 years negotiation between the Maharaja and the British. The lease indenture granted full right, power and liberty the Secretary of State for India to construct make and carry out on the leased land and to use exclusively when constructed, made and carried out, all such irrigation works and other works ancillary thereto to. The agreement gave 8000 acres of land for the reservoir and another 100 acres to construct the dam. The tax for each acre was 5 per year. The lease provided the British the rights over "all the waters" of the Mullaperiyar and its catchment basin, for an annual rent of 40,000.

In 1947, after Indian Independance, the lease agreement expired. After several failed attempts to renew the agreement in 1958, 1960, and 1969, the agreement was renewed in 1970 when C Achutha Menon was Kerala Chief Minister. According to the renewed agreement, the tax per acre was increased to 30, and for the electricity generated in Lower Camp using Mullaperiyar water, the charge was 12 per kiloWatt per hour. Tamil Nadu uses the water and the land, and the Tamil Nadu government has been paying to the Kerala government for the past 50 years 2.5 lakhs as tax per year for the whole land and 7.5 lakhs per year as surcharge for the total amount of electricity generated.The validity of this agreement is under dispute between the States of Kerala and Tamil Nadu. The matter is currently pending before a Division Bench of the Supreme Court.

 

Construction

In May 1887, construction of the dam began. As per "The Military Engineer in India" Vol II by Sandes (1935), the dam was constructed from lime stone and surkhi (burnt brick powder and a mixture of sugar and calcium oxide, one of the archaic construction techniques of 19th century) at a cost of 104 lakhs, was 173 feet high and 1241 feet in length along the top and enclosed more than 15 thousand million cubic feet of water. Another source states that the dam was constructed of concrete (no real evidence or reference for this) and gives a figure of 152 feet height of the full water level of the reservoir, with impounding capacity of 10.56 thousand million cubic feet along-with a total estimated cost of 84.71 lak.

The construction involved the use of troops from the 1st and 4th battalions of the Madras Pioneers as well as Portuguese carpenters from Cochin who were employed in the construction of the coffer-dams and other structures.The greatest challenge was the diversion of the river so that lower portions of the great dam could be built. The temporary embankments and coffer-dams used to restrain the river waters were regularly swept away by floods and rains. Due to the coffer dam failures, the British stopped funding the project. Officer Pennycuick raised funds by selling his wife's jewelry to continue the work. In Madurai, Major Pennycuick's statue has been installed at the state PWD office and his photographs are found adorning walls in peoples homes and shops. In 2002, his great grandson was honoured in Madurai, a function that was attended by thousands of people.

The dam created a reservoir in a remote gorge of the Periyar river situated 3,000 feet above the sea in dense and malarial jungle, and from the northerly arm of this manmade waterbody, the water flowed first through a deep cutting for about a mile and then through a tunnel, 5704 feet in length and later through another cutting on the other side of the watershed and into a natural ravine and so onto the Vaigai River which has been partly built up for a length of 86 miles, finally discharging 2000 cusecs of water for the arid rain shadow regions of present-day Theni, Madurai District, Sivaganga District and Ramanathapuram districts of Tamil Nadu, then under British rule as part of Madras Province (Sandes, 1935).

The Periyar project, as it was then known, was widely considered well into the 20th Century as "one of the most extraordinary feats of engineering ever performed by man". A large amount of manual labour was involved and worker mortality from malaria was high. It was claimed that had it not been for "the medicinal effects of the native spirit called arrack, the dam might never have been finished". 483 people died of diseases during the construction of this dam and were buried on-site in a cemetery just north of the dam.

Protected area

The Periyar National Park in Thekkady, a Protected area of Kerala, is located around the dam's reservoir, the 26 km² (10 sq mi) Periyar lake. 62 different kinds of mammals have been recorded in Periyar, including many threatened ones. Periyar is a highly protected tiger reserve and elephant reserve. There are an estimated 53 tigers (2010) in the reserve. Tourists come here to view the Indian elephants in their natural habitat. The elephant number around 900 to 1000 individuals. Other mammals found here include gaur, Bison, sambar (horse deer), barking deer, mouse deer, Dholes (Indian wild dogs), mongoose, foxesand leopards. Also inhabiting the park, though rarely seen, are the elusive Nilgiri tahr. Four species of primates are found at Periyar - the rare lion-tailed macaque, the Nilgiri Langur, the commonlangur, and the Bonnet Macaque. According to a report by the Kerala Forest Research Institute, the protected area surrounding the dam and reservoir is classified as a biodiversity hot spot.

Safety Concerns

After the 1979 Morvi Dam failure which killed up to 25,000 people safety concerns of the aging Mullaperiyar dam's leaks and cracks were raised by Kerala Government. A State agency, Centre for Earth Science Studies (CESS), Thiruvananthapuram, had reported that the structure would not withstand an earthquake above magnitude 6 on the Richter scale. The dam was also inspected by the Chairman, CWC (Central Water Commission). On the orders of the CWC, the Tamil Nadu government lowered the storage level from 142.2 feet to 136 feet, conducted safety repairs and strengthened the dam. Construction of a new dam was proposed by the CWC but was not pursued.

Current safety concerns hinge around several issues:

• A- Risk /Threat Factors

1. Age of the dam: The dam is 116 years old as of 2011. It has outlived its expected life span of 50 years . Strengthening the existing dam has its limitations and may not prove to be effective in the event of a disaster (reference: Morvi Dam)
2. Construction Material: The dam was constructed using stone ruble masonry with lime mortar grouting following prevailing 19th century construction techniques that have now become archaic. Seepage and leaks from the dam have caused concern.
3. Earthquakes: The dam is situated in a seismically active zone . An earthquake measuring 4.5 on the Richter scale occurred on June 7, 1988 with maximum damage in Nedumkandam and Kallar (within 20 kms of the dam). Several earthquake tremors have occurred in the area in recent times. These could be reservoir-induced seismicity, requiring further studies according to experts. CESS, IIT Roorkee and IISc have reported that the dam cannot withstand earthquakes above 6 point on the Richter scale.
4. Global warming and changing weather patterns leading to incessant rains, flooding and overflow of the dam: Determination of the Probable Maximum Flood and Probable Maximum Precipitation parameters for the dam, is important to ensure dam safety.
5. Inadequate safety maintenance and safety monitoring of the dam

• B- Negative impact of dam collapse

1. Loss of human life and property by catastrophic flooding
2. Loss of flora and fauna including identified endangered species in the Periyar Wildlife Sanctuary.
3. Loss of tourism: Thekkady Reservoir and Periyar Wild Life Sanctuary are important and popular eco-tourism revenue sources in Kerala.
4. domino effect of collapse of Idukki Dam and the disastrous consequences of an Idukki Dam disaster
   
5. Loss of agriculture irrigation, drinking water supply and power generation in southern Tamilnadu.
6. Huge impact on the general economy of Kerala and Tamilnadu. This includes large unbudgeted private and public expenses of flood cleanup and rebuilding the economy.

Construction of a new dam

Kerala enacted the Kerala Irrigation and Water Conservation (Amendment) Act, 2006 to ensure safety of all 'endangered' dams in the State, listed in the second schedule to the Act. Section 62A of the Act provides for listing in the schedule, "details of the dams which are endangered on account of their age, degeneration, degradation, structural or other impediments as are specified" The second schedule to the Act lists Mullaperiyar (dam) constructed in 1895 and fixes 136 feet as its maximum water level. The Act empowers Kerala Dam Safety Authority (Authority specified in the Act) to oversee safety of dams in the State and sec 62(e) empowers the Authority to direct the custodian (of a dam) "to suspend the functioning of any dam, to decommission any dam or restrict the functioning of any dam if public safety or threat to human life or property, so require". The Authority can conduct periodical inspection of any dam listed in the schedule.

In pursuance of Kerala's dam safety law, in September 2009, the Ministry of Environment and Forests of Government of India granted environmental clearance to Kerala for conducting survey for new dam downstream^.Tamil Nadu approached Supreme Court for a stay order against the clearance; however, the plea was rejected. Consequently, the survey was started in October, 2009. On Sept. 9, 2009 stated it had already communicated to the Government of India as well as to the Government of Kerala that there is no need for construction of a new dam by the Kerala Government, as the existing dam after it is strengthened, functions like a new dam.