Mullaperiyar–A dam of controversies

Mullaperiyar Dam is a masonry gravity dam over River Periyar, with a height of 155 feet and length 1200 feet and is located 2889 feet above m.s.l. on the High Ranges (Cardamom Hills) of Western Ghats in Thekkadi, Idukki District of Kerala, India. It was constructed in 1895 by the British Government, over the headwaters of the west-flowing Periyar River and its tributary Mullaiyar, to divert water eastwards to Madras Presidency area (the present-day Tamilnadu). The Periyar National Park, Thekkady is located around the Periyar reservoir formed by the backwaters of this dam. The dam is operated by the Government of Tamil Nadu based on a 999-year lease agreement made during erstwhile British colonial rule, between the British Government (Madras Presidency) and the Travancore Maharajah.

The catchment areas and river basin of River Periyar downstream include five Districts of Central Kerala, namely Idukki, Kottayam, Ernakulam, Alappuzha and Trissur with a total population of around 3.5 million. Water diverted eastward flows through a tunnel from the dam, joins River Vaigai in Tamilnadu, and is used for irrigation and power generation in Tamilnadu. The Periyar Power Station in Lower Periyar, Tamilnadu generates hydro-electricity from the diverted waters. The dam has been a bone of contention between the State Governments of Kerala and Tamilnadu, with Tamilnadu demanding raising of water level in the reservoir to increase flow of water to Tamilnadu, and Kerala objecting to this on the grounds of safety of the 116 year old reservoir that is built using lime and surkhi mortar. Earthquakes in the area have further highlighted safety issues and concerns. Various issues are still being adjudicated by the Supreme Court of India.

 

Periyar river originates in the Sivagiri Hills of the Western Ghats in Kerala, flows northwards and at Thekkady joins the west-flowing Mullaiyar, also originating in the Western Ghats in Kerala. The Mullaperiyar dam is constructed at the confluence of both the rivers Periyar and Mullaiyar to create the Periyar reservoir. From Periyar Thekkady reservoir, water is diverted eastwards to Tamilnadu via a tunnel enabling the water to join the Vaigai River. From Periyar Thekkady Reservoir, the Periyar river flows northwestward into the Idukki reservoir formed by the Idukki, Cheruthoni and Kulamavu dams. From Idukki reservoir, Periyar river flows northwestwards and then westward to join the Arabian sea at Munambam near Kodungallur and the Vembanad lake at Kochi.

 

History of the Dam

On 29 October 1886, a lease indenture for 999 years was made between Maharaja of Travancore, Vishakham Thirunal and 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 (under British rule) J C Hannington. This lease was made after constant pressure on Travancore King by the British for 24 years. The lease indenture inter alia granted full right, power and liberty 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 Secretary of State for India (now Tamil Nadu). The agreement was to give 8000 acres of land for the reservoir and another 100 acres to construct the dam. And the tax for each acre was 5 RS per year. When India became independent, the lease got 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 30 RS, and for the electricity generated in Lower Camp using Mullaperiyar water, the charge was 12 RS per kiloWatt per hour. This was without the consent of the Legislative Assembly of KeralaThis agreement expired in 2000. However, Tamil Nadu still 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 Rs as tax per year for the whole land and 7.5 lakhs RS per year as surcharge for the total amount of electricity generated

 

The first dam was built by the British Corps of Royal Engineers. After the first dam was washed away by floods, a second dam was built in 1895. it is built with stone and Surki ( A mixture of sugar and Calcium oxide).
The construction work on a small dam began in 1850 but was abandoned. This was because of fever among workers and demand for higher wages. In May 1882, the work on the dam resumed and was entrusted to Major John Pennycuick. It's total estimated cost was Rs. 84.71 lakhs. The reservoir was to have a height of 152 feet and a capacity of 10.56 thousand million cubic feet.

The dam's purpose was to divert the waters of the west-flowing Periyar River eastward, taking the water from the reservoir through a tunnel cut across the watershed and Western Ghats to the arid rain shadow regions of Theni, Madurai District, Sivaganga District and Ramanathapuram districts of Tamil Nadu. Although Kerala claims that the agreement was forced on the then princely State ofTravancore, presently part of Kerala, the pact was re-validated in 1970 by Kerala and Tamil Nadu. The lease provided the British the rights over "all the waters" of the Mullaperiyar and its catchment basin, for an annual rent of Rs. 40,000.

 

The Periyar dam is the first Surkhi concrete dam in a “V” shaped gorge in the Western Ghats over the west flowing Periyar river.  This Periyar river is a perennial river which rises from the Sivagiri group of hills in Kerala state and flows through Kerala state and joins the Arabian sea.  Out of its total catchment of 4976 sq.km only 114sq.km at the origin of the river lies in Tamil Nadu.  It is built of concrete in Surkhi motor (brick powder in lime) with a thick masonry facing and is 173m high above foundation rock with a base width of 144.5ft Its length is 200ft at foundation level and 1241 ft at top.  On both sides of the main valley there are smaller depressions and the one on the left side was blocked by a second dam of the same time with 221ft length and 53ft height which is connected with the high ground by means of an earthen dam.  The depression on the right flank is utilized as an escape channel and it was originally cut down to a level 11ft below the crest of the main dam and it functions as an open weir escape for discharge of  flood flows.  But doubts were expressed about the spillway capacity during heavy floods and in 1908 the level of the escape was reduced by 8ft and a regulator was constructed upon it with 10 spans each of 36ft width, fitted with gates of 16ft height.  There is an extremely huge quantity of Dead Storage provided merely to raise the remainder water to the level at which it can be passed through the tunnel into the Eastern side of the river basin watershed.  The level of the sluice through which the water drawn by the Tamil Nadu is 48ft below the crest of the dam which leaves a Dead Storage water depth of 125ft When full, the lake holds 15.661 TMC  of water out of which 9.176 TMC is utilizable as it is lying above the level of the sluice. From the Northern most arm of the reservoir the water is led for about a mile through a deep open cut channel and then through a tunnel of 5700ft length into another open cut channel on Eastern side of Western ghats which leads into the Surulivar rivulet which discharges into Vaigai river.  After irrigating about 1,27,000 acres in the Surulivar river valley the water is picked up at the Perani regulator across the Vaigai river about 80 miles downstream of the tunnel and flows into the Periyar main canal of 35 miles length.   The main canal of 35 miles length is 100ft wide at its head and discharges 2000 cusecs of water.  The rainfall occurs in 4 out of 5days during June to November when the rain is practically continuous.  Sudden floods from 10,000 to 1,20,000 cusecs are constantly experienced during most of the year.  Sometimes 3 inches of rain is recorded in a period of 4 hours ,resulting in heavy floods.  The project sanctioned in 1884 and started in 1887 was completed by 1897.  Where formerly 66,000 acres of land in Tamilnadu was irrigated from scanty and unreliable water sources 1,85,000 acres was provided with unfailing water supply at a cost of Rs.1.048 crores and the project returns about 6% on capital outlay and proved a financial success.

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