Opinion | In Kerala, dammed if you do, dammed if you don’t
With the likelihood of extreme weather patterns increasing because of global warming, operational management of dams deserves equal importance
The rain in Kerala this monsoon has been relentless. From 1 June to the third week of August, the state received nearly 2,400 millimetres of rainfall—an excess of 41%. Thirteen of its 14 districts (except for Kasaragod in the north excess rainfall, with Idukki (+92%) and Palakkad (+72%) recording the highest deviations. In particular, two episodes of deluge—the first in June and the second in August—tipped the balance from normal to disastrous, with the excess rain being carried in torrents to the Arabian Sea by Kerala’s rivers.
Kerala has 41 west-flowing rivers out of a total of 44. These rivers—rivulets really—are mostly rain-fed and have steep gradients as they drop 2,000m from their source in the Western Ghats to sea level over short distances of about 200km. The main rivers—Periyar, Bharatapuzha, Pamba, Chaliyar and Chalakudy—run mostly through central Kerala and finish up in Kerala’s famous backwaters. Given the gradient and the monsoon flow, there are 42 large dams on these rivers. Under normal conditions, these dams, such as the Idukki, Parambikulam, Idamalayar, Mullaperiyar and Malampuzha, provide much-needed water for electricity and irrigation. Nearly all of Kerala’s electricity is hydro-electric.
August 2018 was not normal. On the back of two weeks of incessant rain, for the single 24-hour period starting 15 August, many weather stations in Kerala recorded 300-400mm of rain. For a state where the urban-rural continuum is fluid, the water really had nowhere to go except through hamlets and towns and down river beds and roads. Armed with remittances from the Gulf countries, the householders of Kerala have cropped trees and shrubs in a fierce attempt to corner all land available for housing. This baldness led to a series of landslides that probably led to most of the fatalities.
With years of deficient rain to shape their thoughts, dam managers in Kerala and Tamil Nadu (Mullaperiyar is managed by the Tamil Nadu government), chose to conserve water in the reservoirs until the very last moment. Thereafter, in the interest of dam safety, they had little choice but to release water in large quantities, flooding vast areas downstream and inundating townships built on the flood plain. Kochi airport, set on the flood plains of the Periyar, in the town of Nedumbassery, has the dubious distinction of being shut down for the longest period of any airport in India because of being flooded.
All this is eerily reminiscent of the flash floods that occurred in Chennai in December 2015. Then, the Adyar river, usually not much more than a drain, flooded the city, bringing misery in its wake. In similar fashion, the city was flooded because of an extreme weather event combined with reservoir and dam flow mismanagement. A Comptroller and Auditor General of India report released earlier this year points to an “injudicious decision to release large quantities of water” as the proximate cause of that disaster. The Kerala floods this year, when fully studied, will likely point to many causes. Of these, the most important reasons will likely be excess rain, deforestation in the Western Ghats, years of deficient rain leading to facilities and townships being located on flood plains and reservoir and dam mismanagement.
As reported widely, the disaster response from the government, armed services, fishermen, communities and citizens from other states has been exemplary. Disaster preparedness on the other hand has been downright disastrous. Since there have been no major floods in Kerala since independence, it has no flood warning system. The Central Water Commission (CWC), which issues such alerts, does not have the ability to monitor and issue alerts for “small river flash floods”. Though Kerala’s floods occurred over the entire state, they were really a series of small river floods.
Furthermore, the carrying capacity of these rivers has been reduced significantly due to silting.
Dam management has been very “engineering-oriented” in its approach, with dam safety and reservoir heights emphasized over a more holistic and integrated approach that would include weather simulation, land use on the flood plain and community preparedness. Dam safety is of course paramount—India has had 33 dam failures since independence and 80% of the dams are more than 25 years old. Spillway capacity may need to be re-evaluated for several dams if they are to do the job in normal and extreme conditions. However, with the likelihood of extreme weather patterns increasing because of global warming, operational management of dams deserves equal importance. Going by this month’s events, none of Kerala’s dams had a disaster action plan.
For dams to do their jobs in extreme situations, they should have large unfilled capacity in their reservoirs when extreme events occur. Decision systems must, therefore, de-emphasize a scarcity mindset and replace it with scientific weather simulations that inform prudent management. The most likely form this prudent management will have to take is for steady release of water, even at the risk of not filling the reservoir at the end of the monsoon. Otherwise, dams will exaggerate and amplify extreme weather events. For the Kerala floods of 2018, dams did just that.
P.S. “The river flows at its own sweet will, but the flood is bound in the two banks. If it were not thus bound, its freedom would be wasted,” said Vinobha Bhave.
Narayan Ramachandran is chairman, InKlude Labs. Read his earlier columns at www.livemint.com/avisiblehand
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