SUBMERGE the polemics, legal tangles and conflicting technical claims, and the participants in the inter-State dispute over the Mullaperiyar dam – one of the oldest and highest ‘solid masonry gravity dams' in the world – will no longer be able to ignore the anxiety and panic that the 116-year-old structure has created among the people in Idukki, especially, and four other districts in Kerala.

The spontaneous initial outpouring of the people was followed by unusual protests demanding the decommissioning of the dam in the wake of intense rain and repeated low-intensity tremors in Idukki district, at locations over 30 kilometres away from Mullaperiyar, on November 18 and 26.

Following seasonal rains in the catchment areas of the dam, the reservoir was fast filling up when the first of the quakes occurred, and the spillway level of 136 feet (41.45 metres) was crossed within a few days.

The dam filled to capacity and the series of “minor” earthquakes activated an unprecedented unity of purpose in Kerala. Ever since the detection of fresh leaks on the dam's surface in 1979, people have demanded that the water level in the reservoir be lowered and a new dam be built.

The protests have taken the form of silent marches, hunger strikes, hartals and ‘human walls' in the five districts through which the Periyar flows, and other State-wide campaigns, some involving violence. The State government, on its part, demanded immediate mediatory and legal remedies from the Centre and the Supreme Court.

Mullaperiyar is the first in a series of hydroelectric and irrigation projects across Kerala's longest river, the Periyar, which originates in the Western Ghats and drains into the Arabian Sea and the backwaters near Kochi. Tamil Nadu, across the Western Ghats, is the sole beneficiary of the British-built dam and it is against any further reduction in the water level in the reservoir. Instead, it wants the level to be raised to 142.40 ft (43.4 m), as an interim measure, and further to 152 ft (46.32 m), as per the recommendations of a committee of the Central Water Commission (CWC) that examined the dam nearly two decades ago and suggested several measures to strengthen it.

By constructing the dam in the deep jungles of the Western Ghats, about 2,800 ft (853 m) above sea level, the British rulers of the then Madras Presidency had, from 1895, diverted the West-flowing Periyar river across the Ghats to the east, through a 5,704-feet (1,738.5 m) tunnel that opened into a tributary of the Vaigai river in the then Madurai district. This remarkable engineering feat achieved with the hard labour of mostly Indian workers today sustains irrigation and drinking water supply in five districts of southern Tamil Nadu. (The Periyar is also known as the Mullaperiyar, after a tributary, the Mullayar, joins it about 50 km from its origin in the Sivagiri Hill, east of Peerumedu.)

Though the dam is located in Kerala, it is controlled, managed and operated by Tamil Nadu, under a lease agreement of 1886 between the British and the erstwhile Travancore State, and validated subsequently by Kerala and Tamil Nadu in 1970.

The original agreement gave the British the right over “all the waters” of the Mullaperiyar and its catchment for diversion to the British territory (now Tamil Nadu) for 999 years. The waters of a river with about 5,284 square kilometres (out of a total of 5,398 sq km) of its catchment area in Kerala, stored in a reservoir within Kerala territory, thus came to be used exclusively by the people of southern Tamil Nadu from 1895 onwards, when the diversion project was inaugurated. According to one estimate, over 70 lakh people in Tamil Nadu's Theni, Dindigul, Madurai, Sivaganga and Ramanathapuram districts today depend on the waters of the Mullaperiyar reservoir (the scenic Thekkady lake) for the irrigation of about 2.5 lakh acres (1 acre = 0.4 hectare) and for drinking water needs. The (upper) Periyar has thus transformed a once-drought-prone region in the southern part of Tamil Nadu into breathtaking green valleys, vineyards and rich fields growing paddy, banana, coconut and a variety of vegetables and fruit. Since 1970, Tamil Nadu has been using the water to generate 140 megawatt (MW) of electricity as well.

In 1979, Tamil Nadu was forced to reduce the water level in the reservoir after detection of leaks in the dam. However, its requirement of the Periyar waters for irrigation had only been increasing year after year. The total irrigated area in the Periyar-Vaigai basin has expanded substantially, leading to a quantum jump in the water required from the reservoir. Farmers' groups in Tamil Nadu area have demanded that the Mullaperiyar water level be raised and “new channels” be opened from the Periyar system for irrigating new areas.

During most of the Periyar project's early history, the section of Kerala falling on the downstream areas of the reservoir seemed to have remained generally a water-surplus region, with plenty of rain (and meagre population in the Ghat areas). But from the late 1970s, soon after Kerala constructed the Idukki hydroelectric project 50 km downstream of the Mullaperiyar dam and denudation and encroachment of the surrounding areas increased, the State too began to feel the pinch. But it could not use (particularly during summer) even a wee drop from the huge source of water within its own territory.

For most part of the year, no water flowed from the Mullaperiyar reservoir to Kerala even as the population in the valleys between the Idukki and Mullaperiyar dams too began to increase. Almost all the water that reached the Idukki reservoir for most part of the year was only from the catchment areas downstream and from the Periyar's tributaries.

Safety concerns

The detection of leaks in the Mullaperiyar dam in 1979 had led to concerns about the dam's safety even though the reservoir level was brought down to 136 ft. Minor earthquakes were regularly reported in the region, and by the 1990s, Kerala government representatives, in private conversations, began expressing bitterness at the insensitivity of Tamil Nadu to the security concerns in Kerala. “Whether any State can rely permanently on the resources of another State” was a question that began to be raised, but at no time was there a demand that the Periyar waters be denied to Tamil Nadu.

A senior adviser to the State government on Inter-State River Water Disputes put it succinctly to Frontline in October 1998, when the dispute had reached a new low: “The case of the Mullaperiyar dam is peculiar in that the beneficiary is comfortably situated elsewhere and the donor stands to face the peril if something happens. Some experts have said the dam is safe. But can any government afford to throw caution to the winds?”