Kerala is facing anxious moments with recurring earthquakes in Idukki district and the waters of the 116-year-old Mullaperiyar dam at the spillway level. However, the preparedness of the State for a dam failure is far from adequate. It has so far not done a dam break analysis and inundation study keeping the possibility of failure of Mullaperiyar and Idukki dams in view.
Belatedly, the State has now decided to commission a study by IIT, Rourkie, and agreement for this was signed in Delhi on Wednesday. Such a study report would have been important for the State in arguing its case before the Supreme Court, if it had been done in time.
The Court had observed that while allowing Tamil Nadu to raise the water level of the Mullaperiyar reservoir that water from Mullaperiyar reservoir would be contained in Idukki reservoir if Mullaperiyar dam failed. While this is factually incorrect for all situations, Kerala had even failed to point out that there were around 75000 persons living in the area between the two dams. In fact, even today the government does not have a correct estimate of the area that would be inundated in case of a failure of the dam, the population in the area, distances and the response time that each locality would get.
There is also no idea about safer places to which populations could be effectively moved within the response time available. In many countries such studies have become mandatory. When questions about this was raised at a recent press conference of the Water Resources Minister P. J. Joseph, the answer from a scientist of the Centre for Earth Science Studies was that they had not completed their study on this. It could take waters from Mullaperiyar four to six hours to reach the Idukki dam "according to some authoritative sources," he said giving the impression that he himself was not sure of that.
Mr. Joseph said that in case of failure of Idukki dams, the people of Ernakulam district would have nowhere to run to. There was little point in planning for disaster management for such an eventuality. And this eventuality will be real in the case of failure of Mullaperiyar dam if the Idukki dam nearly is full.
The Mullaperiyar dam currently has more 11 tmcft of water while Idukki dam is short of only 10 tmcft to reach full reservoir level. It is obvious that the waters from Mullaperiyar would not be contained in Idukki reservoir under the present situation. The spillways on the Cheruthonic dam of the Idukki reservoir would not be able to handle the flow if the water level is higher. More than that, there is the possibility of large quantities of earth and debris landing in Idukki reservoir leading to overtopping of the dam.
Floating trees could damage and clog the spillways. Even if the dams of Idukki survive, the reservoir would be rendered practically useless by silt. It may be noted that inadequacy of spillway capacity has been one of the major reasons for failure of dams in the World. The spillway capacity of Idukki reservoir is not considered adequate to meet the combined probable maximum flood in the catchments of Mullapperiyar and Idukki dams.
The government came alive to the need to clear the blocks and debris behind the spillways of Mullaperiyar only after water reached the spillway level overnight this week. With water flowing over the spillways, the work became difficult. In fact, experts had recommended long back that a certain slope should be ensured along the flat area behind the spillways for efficient discharge of water. (The spillways of Mullaperiyar are a separate structure and a flat stretch of land separates it from the water in the reservoir until the level reaches 136 feet). This is yet to be carried out.
In case of failure of Mullaperiyar, opening of the spillways, emptying of water and measures to protect the Idukki dam will assume paramount importance. Effective reduction of water is to be achieved in a few hours. However, even communication and quick response systems are absent both at Mullaperiyar and Cheruthoni except for some interim arrangement made by the district collector a few days ago. Many of the instrumentation for measuring parameters such as stress and strain on the dam are either absent or defective at both locations.
The government has asked A. V. George, head of the Department of Geology and Environmental Sciences of Christ College, Iringalakkuda, in 2007 to undertake a study on disaster management, in case of failure of the dams. However, it did not make much progress because of lethargy of the Irrigation Department and objections from Finance Department.
A proposal to establish a network of digital Seismometers met with a similar fate. Now, the State Electricity Board takes hours to determine epicentres of tremors, especially when it happens at night as graphs are to be fetched manually from the seismic stations. Information about epicentre of quakes and their magnitude is important information for those overseeing rescue and relief operations in the event of earthquakes.
