Monitoring dam safety

Decommissioning should be a policy option

Even after the enactment of the Dam Safety Act in 2021, the threat to the life, property, and livelihood of millions of people from dam-related perils remains unabated. This is clear from the latest report of the Parliamentary Standing Committee on Water, which points out though 234 large dams are 100-300 years old, none has been decommissioned. In fact, retiring a dam has seldom been deemed an option in India even if the structure turns highly hazardous — as is the case with the nearly 130-year-old Mullaperiyar dam, which is not being replaced with a new one despite having been declared unsafe by the Kerala government. Decommissioning vulnerable dams is now common practice to avert dam-related disasters in developed countries, notably in Europe and the US. India, too, should follow suit, paying heed to the parliamentary panel’s sane counsel in this regard.
 

With more than 5,740 large dams and countless other barrages, India is now placed third in the world, next to China and the US, in terms of the number of functional dams. The disquieting part, however, is that nearly 20 per cent of them have outlived their rated life span of 50 years. Besides, most of these old dams were constructed with locally available material and in accordance with the water flows and risk factors prevailing at that point of time. The situation has since undergone a dramatic change because of a further development of the water-use infrastructure and global warming-induced uncertainties of the volume of water flows. Risk factors like flash floods, landslides, and increased sedimentation are much more pronounced now than in the past. Little surprise, therefore, that the country has witnessed more than 40 major dam failures in recent decades. The latest major calamity was in February 2021 in Chamoli district, Uttarakhand, where one dam was swept away by gushing water from a dislodged glacier and another one, on the downstream, was partly damaged, resulting in 140 deaths, apart from damage to property, infrastructure, and crops. The biggest ever disaster was, perhaps, the caving in of the Machchu Dam in Gujarat on August 11, 1979, which annihilated the densely populated industrial town of Morbi and many of its neighbouring villages.
 

It is, therefore, imperative to evolve a mechanism, as recommended by the parliamentary panel, to precisely estimate the potential life span of dams and decommission the over-aged ones to minimise the risk of their crashing down. Oddly enough, the jal shakti ministry conceded before this parliamentary committee that it did not have any methodology to assess the viable lifetime of dams. Routine maintenance work is done on the basis of the health evaluation of the structure. This is a grave lacuna that needs to be addressed without delay. One way of doing so could be to follow the US system of risk appraisal through a web-based integrated risk management model — called Dam Safety Analysis Tool — using variables from dam bursts in the past. It generates a fairly reliable prognosis of downstream risks of dam failures. The other, and preferable, possibility could be to develop an indigenous system for this purpose, using the expertise available in scientific institutions like the Indian Institutes of Technology. Such hi-tech models for monitoring dam safety would be of great help in pre-empting, and preventing, dam-related mishaps.