Southwest monsoon's shockingly deviant behaviour was first noticed in 2018, the year of the deluge.
In the August of 2018, most districts in Kerala received a 100-180 per cent excess monsoon rain with devastating consequences. This was considerably more rain than was ever witnessed during the usual rain months of June and July.
This was then seen as an aberration, a freak event. In the four August months before 2018, there was a rainfall deficit; in 2015 and 2016 the deficit was 49 and 39 per cent respectively. Traditionally, therefore, August was the time the southwest monsoon began to lose its steam, showed signs of panting.
Deadlier monsoon variant
However, 2019 and 2020 demonstrated that the 2018 'August explosion', which disaster management officials informally call the 'Onam curse', was no one-off event.
Both these years saw a rainfall excess in August that matched that of 2018 August; in fact, the 2019 excess was far more drastic in many districts than in 2018. It was as if the monsoon had mutated into a deadly new variant. Monsoon, it was felt, was transforming into a different beast; coming alive late, only by August, but playing around with a ferocity unheard of.
Yet, if Kerala did not suffer total destruction during August in these two years like in 2018, luck seemed to have played a big part. The monsoon was feeble in June and July during both 2019 and 2020. This was not the case in 2018 when June and July saw huge and incremental rainfall excess: 24 per cent for June and 64 per cent for July.
It also helped that the KSEB, after the clumsy work in 2018, had learned to manage the water level in its dams more efficiently.
Why a 2021 August explosion is dangerous
This year also, as has been the norm in the last two years, the southwest monsoon has been weak during June and July, giving rise to fears that the phenomenon was waiting to explode in August like in the last two years.
An 'August explosion' this year could be dangerous for Kerala. “Though the monsoon spell till now has been weak, Kerala had received some heavy summer showers and our dams hold more water than is seen as comfortable during August. So a massive burst of rain in August remains a threat,” said M Seetharaman, a professor of atmospheric studies.
Since there was a large excess of summer rainfall this time, 108 per cent, Kerala's dams are more filled than in 2019 and 2020. In 2019, at this point, Kerala's dams were just 19 per cent full. In 2020, it was 49 per cent full. However, this year, they are 65 per cent full.
Empty space strategy
Of relief, however, is the fact that the water level in none of KSEB's dams has reached a level at which even the first level of alert, the Blue Alert, has to be sounded. Take for instance Idukki dam, Kerala's largest. On August 6, the water level in the Idukki reservoir is 2370 ft; the blue alert will be sounded only at 2375.53 ft, orange alert at 2381.53 ft and red alert at 2382.53 ft.
After the 2018 tragedy, and the grave charge that the KSEB had failed to ensure the controlled release of water from the quickly fattening dams in 2018, a new system called 'Rule Curve' has been developed. “The Rule Curve ensures that at no point the water level in any of our major dams will reach anywhere near danger levels,” a top KSEB official said. “If there is excess inflow, there will be controlled release from the dam to keep the water level at desirable levels. We have not even reached a stage where we have to do the controlled release in any of our dams,” the official added.
Improbability of the curse
The 'August explosion', or the 'Onam Curse', looks remote at this stage. The Indian Meteorological Department had not put out any ominous forecast for the first quarter of August; it was between August 5 and 15 that the southwest monsoon had gone berserk in the last three years. The IMD, though it has said there would be an even distribution of rainfall, has not forecast anything more than 'moderate rainfall' till August 10.
At this stage, on August 6, Kerala has a monsoon deficit of 28 per cent. All the districts that had suffered in August in the last three years - Idukki, Pathanamthitta, Wayanad, Kottayam, Alappuzha and Palakkad - have recorded a monsoon deficit.
“This means there is no burden of dormant water on our hills that with a sudden extreme event like a cloudburst could detonate our hills. Therefore, with a certain amount of certainty we can rule out landslides this time,” a top Kerala State Disaster Management Authority official said on condition of anonymity.
The monsoon deficit is highest in Palakkad, 40 per cent. In Wayanad, where heavy rainfall had triggered innumerable landslides and washed away 17 people at Puthumala in August 2019, the deficit is 38 per cent; in August 2019, Wayanad was battered by a monsoon excess of 110 per cent.
In Idukki, where 63 plantation workers were swept away by a landslide on August 7, 2020, the rainfall deficit is 25 per cent; in August 2020, there was 45 per cent excess monsoon rainfall.
In other words, even if there is a sudden burst of August rainfall this time, vulnerable districts are in a position to absorb the shock.
