The Centre's approval to Kerala for conducting a survey to build a new dam across Periyar river to replace the 113-year-old reservoir has intensified the long standing row between the state and Tamil Nadu.
Upstream Kerala has been persistently raising the pitch for a new dam, citing safety concerns over the structure built in 1895, while Tamil Nadu is opposed to the move, insisting the existing reservoir was strong enough and had even won a legal battle to increase the storage level.
Kerala apprehends severe threat to the safety of life and property of four million people living downstream the dam located in Idukki district of the state.
Citing experts report, it had pointed out that the dam, which feeds over 68,000 hectares in southern Tamil Nadu, is located in a seismic prone area where a couple of low-intensity quakes had been reported in the last few years.
The dam was built in highrange Idukki district when the area was under the erstwhile princely state of Travancore, before the formation of the present Kerala state in 1956.
Under the lease agreement for 999 years, much of the water from the reservoir, under Tamil Nadu's control, would be diverted to parts of state like Theni and Periyakulam.
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The dispute between the two states began in mid-1990s when Tamil Nadu started demanding raising the maximum water storage from 132 feet to 138 ft in the first phase and then to 142 ft and then the full level of 152 ft.
Tamil Nadu has buttressed its claim on the basis of inspections by Central Water Commission. But this had been stiffly opposed by Kerala.
Later, Kerala reinforced its claim on the weakness of the dam based on studies by experts team from IIT Roorkie. The states own experts committee had often reported seepage opening at several points on the downstream side of the concrete backing of the structure.
Since no amount of repairs can salvage the lime and surkhi dam anymore, the only viable engineering solution to avoid a 'looming danger' is to construct a new dam, Kerala contends.
In the wake of the Supreme Court delivering judgement in February 2006 allowing Tamil Nadu to raise the water level, Kerala Assembly passed a dam safety legislation, empowering the government to decide on matters relating to water level of any dam in the state and de-commissioning any existing one. This has been challenged in the apex court by Tamil Nadu.
After the Union Forest and Environment Ministry last month gave its clearance, Kerala on October 19 commenced work on the survey and investigation in those portion of the proposed site coming under the Periyar Tiger Reserve, intensifying the dispute between the two states.