Four moderate tremors that occurred on Saturday in the catchment area of Mullaperiyar dam in Kerala have raised serious concerns about the safety of the 116-year-old dam.
So far, 23 tremors ranging from 2.4 - 3.8 on the Richer scale had been recorded in Idukki district during last 12 months. The tremors on Saturday occurred in some parts of the nearby Kottayam district.
A study conducted by IIT-Roorkey said the dam could collapse if an earthquake of 6 and above hits the area.
Collapse of the dam may result in around 4 million people in Idukki, Ernakulam, Kottayam, Alappuzha and Thrissur districts losing their lives.
According to sesmolgical experts, an earthquake in the magnitude of 6 might occur as moderate tremors occur frequently. Four control rooms have already been opened in the last two days in Idukki as the water level in the dam reached the danger mark. Seepage of water has increased to an alarming level during the last couple of weeks due to tremors. Moreover, there has been heavy rainfall in Idukki district for the last 3-4 days raising the level to 135 feet.
Some of the shutters have already been opened as part of the safety measures. The Kerala government has urged the Union government to intervene in the matter and initiate a dialogue with the Tamil Nadu government. A ministerial delegation from Kerala will meet Union ministers AK Antony and Pawan Kumar Bansal in this regard.
According to a report submitted by N Sasidharan, who was a member of the experts committee to study the present condition of the dam, a 35 feet wide broken area has been formed below the water level of the dam with a length of 1,200 ft, which is a major concern.
The Mullaperiyar dam was constructed over the headwaters of Periyar by the British in 1895. Periyar is the second longest river in Kerala with a length of 244 km. The Periyar National Park, Thekkady, is located around the reservoir formed by the backwaters of this dam.
It is operated by Tamil Nadu, though it is situated within the territory of Kerala, according to a 999-year lease agreement during the erstwhile British rule. The dam has a capacity of 443.23 million cubic metre and provides water to districts like Theni and Madurai in Tamil Nadu.
To ensure safety, Kerala had proposed to construct a new dam, 1,500 ft down the present one without violating the conditions of the agreement signed in 1886 by V Ram Iyengar, the diwan of Travancore, and JC Hannington, secretary of the erstwhile Madras state. But Tamil Nadu not only opposed the proposal, it also wanted the water level be raised to 142 feet.
The Supreme Court then appointed an empowered committee, which instructed the Central Soil and Material Research Station (CSMRS), New Delhi, to find out the conditions of dam especially under the water. Kerala is now demanding the water level be reduced below 120 feet. CSMRS has submitted its report to the empowered committee.
Likely damage
If the dam bursts, the entire water will flow to the Idukki dam, which is the largest arch dam in India, and to other medium dams like Kulamavu, Cheruthoni in Idukki district and Bhoothathankettu in Ernakulam district besides flowing into about 100 small and check dams in both the districts.
Experts say the Idukki dam would not be able withstand such a huge threshold of water. River Periyar and its branches flow through Idukki, Ernakualm, Alappuzha and Thrissur districts and the water level is expected to rise even up to 40 ft in some parts.
