Mercurial Monsoon

The famously capricious rains are reinforcing their reputation every year. Our planners need to take a hand in this Act of God

By SOPAN JOSHI

Its semantic density is comparable to that of a block of reinforced concrete. The India Meteorological Department’s monsoon forecast, updates of which defy comprehension at the best of times, is not the stuff of popular culture. Yet, it addresses the lives of millions of people likely to suffer floods and water logging this monsoon—or, worse still, a drought in the coming year.

It addresses the lives not only of the poor farmers who squat with their hands clasped on desiccated, cracked soil, praying for rain. It matters to the urban rich who want to know whether or not they will have to deepen their borewells this year, or upgrade to more powerful motors to tank up with municipal water before their neighbours beat them to the game. It matters no less to the flood-prone, who once inhabited remote locations like north Bihar or lower Assam, but now live in the posh suburbs of Indian metros. And it matters to the onion farmers of Nashik as much as the hysterical TV news anchors who may not have forgotten last year’s crisis that broke out over onion prices.

The monsoon this year was 10 days too late over the Andamans, three days too early over Kerala, covered the southern states rapidly thereafter, and then took a break of five days. It was five days late over West Bengal and the Northeast, and three days too early over Delhi. On 21 June, the Met Department (IMD) said that rainfall was 11 per cent higher than average, and then went on to forecast a below-normal monsoon. Commodity prices headed north, and the Sensex plateaued, staring southwards.

All this is par for the course. The headlines read the same last year too. What is actually changing, though, does not make it to the headlines. It is what a clutch of boffins has been trying to tell us over the past five years with a series of scientific papers and graphs. It makes for sobering reading: the monsoon is showing extremist tendencies. While the overall amount of water India gets has not changed too much, who gets how much and when is not what it used to be. And, as science figures out our meteorology, the only thing we are learning for sure is that the monsoon is getting increasingly unpredictable.

Nobody knows this headache more intimately than BN Goswami, who, as the director of the Indian Institute of Tropical Meteorology in Pune, has one of India’s least enviable jobs. For, even under the best conditions and at the most scrutable of locations, weather and climate science is notoriously imprecise for numerous reasons. Science establishes variables through constants, and the atmosphere has way too many variables. For another, there is simply too much atmosphere up there—and in three dimensions. For a species naturally denied the power of flight, it is extremely expensive to get real-time data from that high up.

This is where it begins to get tricky. As Goswami explains, all tropical weather is notoriously difficult to predict because winds in the tropics mostly move vertically, a result of the constant heat of the sun (scientists call it convection). Then there is the peculiar geography of India, which has the world’s largest seasonal rain system, the South Asian monsoon, running into the world’s tallest wall, the Himalayan range. Just beyond the Himalayas lies Tibet, which was the southern coast of Asia a long time ago but has been rammed 5 km upwards by the Indian plate. Today, the Tibetan Plateau’s average altitude is about the same as that of Mont Blanc, the Alps’ highest peak. The heating of the Himalayas and Tibet leads to heating at much higher altitudes, and it is now believed that this is what draws in the world’s strongest monsoon.

It stands to reason that global warming due to climate change will change how these factors combine. Higher temperatures mean more evaporation above oceans, which should mean more rainfall for the Subcontinent. So, is rainfall increasing? Is there evidence of global warming affecting our monsoon?

Goswami and his colleagues tried to find out by looking at rainfall data of well over a century. But the graphs showed no change in the amount of total rainfall over India. “There were changes year-to-year,” says Goswami, “Some decades were generally wetter than others. But there was no change in the annual average.” So the Pune team looked closer to sift the rain patterns. They compared rainfall in the period 1951–1970 with that in 1980–2000.

The statistics obliged.

Heavy rainfall (15 cm per day and above) had increased. “It’s not just that we now have more days when there is heavy rainfall,” says Goswami, “Even the intensity of heavy rains has increased.” So, if heavy rainfall is increasing, it is safe to expect that the total amount of rainfall will also increase.

Anything but. Because the number of days with moderate rainfall (below 10 cm) has decreased, cancelling out the increase in days with heavy rain. Goswami’s team looked at data for the whole of Central India. The story was the same for the entire region: more days of heavy rain, fewer days of light rain. “More heavy rains mean more flash floods and natural disasters. Fewer light rains mean greater water stress,” Goswami infers. Water from heavy rains gets washed off, taking the top soil with it; it takes light rains for the water to seep into the soil, to become available as groundwater. This change in the monsoon will alter the Subcontinent’s hydrology, because 70–90 per cent of the water we get is from the monsoon.

The future is flood-prone. It is also vulnerable to chronic drought. And no one can warn Indians whether to prepare for a deluge or build another tank to deal with water scarcity. This is because Goswami’s primary task—predicting the monsoon—is getting impossible. Extreme rainfall (what meteorologists call high-frequency events) form quite quickly and die off even quicker. This is what a weatherman’s nightmare is made of: sudden changes that disappear before they can be observed.

To test the monsoon’s predictability, the Pune meteorologists isolated ‘close analogs’: years in which the amount and pattern of rainfall was similar. The question was: are errors in prediction increasing? The answer lay in calculating how quickly the errors double (in jargon, it is called ‘error doubling time’). They found errors in prediction doubling twice as quickly over the past 25 years. This increase in error is concomitant with the increase in extreme rainfall.

“These extreme events affect our low pressure systems, depressions and cyclones. If there is an error in simulation of these extreme rainfall events, it affects our prediction of lows and depressions, and, ultimately, our ability to predict,” Goswami explains. The uncertainty is frustrating, and what we are learning raises more questions than it answers.

M Rajeevan of the National Atmospheric Research Laboratory in Tirupati knows that only too well. An established name in Indian meteorology, he has studied the impact of climate change on the Indian monsoon. His research shows a decrease in the frequency of monsoon depressions, which bring rain over northern India. He suspects that this is behind the decreased rainfall over east-central India (Jharkhand and Chhattisgarh), where the monsoon’s onset is already delayed by five days on average. Kerala, too, gets less rain now than before, but Maharashtra is getting wetter.

Rainfall distribution has changed over time as well. The month of July does not get as much rain as earlier, but August is getting wetter than ever. Rajeevan says this has serious implications for agriculture and water resource planning. For example, does a dry July mean farmers ought to delay preparing the seed bed and sowing of seeds? Farmers tend to follow an agricultural calendar that is ingrained by tradition and punctuated by religious festivals—so deeply that it is difficult to tell one from the other. Because the monsoon crop, kharif, has always been critical, all religious festivals and weddings come to a halt during the monsoon, and most people do not travel. This has as much to do with needing all hands on the farm as with the belief that the Hindu pantheon go to sleep along with Lord Vishnu for four months.

Going by Rajeevan’s extensive research, should Lord Vishnu review the dates of his monsoonal hibernation? Should farmers review their dates of sowing as well as the crops suitable to the changing monsoon? If farmers change what they sow, will consumers be willing to change what they eat? If Hindu astrologers were willing somehow to compensate for climate change, which climate models should they trust? It is well known that global climatic changes, such as El Nino, influence the monsoon. But each model gives a different account of the relationship. Says Biswas: “The models are all inaccurate.”

Consider the influence of the expected increase in sea surface temperature. It will impact the monsoon, but there is no telling how. It seems likely that global warming will increase precipitation. But how will the melting of polar ice caps influence rains?

The melting of the Arctic ice cap won’t make much difference because it is in the sea (mostly under), but if the ice over Greenland melts, it will be quite another story. It will greatly increase the freshwater content of the northern Atlantic. Freshwater is lighter than the dense sea water, and will lower the temperature of ocean currents and that of the air above. “This cooling may weaken the monsoon,” surmises Goswami.

Factoring in such changes requires not only an exponential increase in the computational capacity of our climate models, but also an infusion of talent in meteorology, not to mention a great increment in observatories to generate weather data, especially over the planet’s oceans. All this requires nothing short of a paradigm shift in how seriously we take meteorology, not to mention the hitherto unimagined investments of money and human resources.

Knowing the monsoon better is worth a lot. Reserve Bank of India Governor D Subbarao said last August that the efficacy of his monetary policy depended on the monsoon. On 14 June this year, he listed the two things that will determine inflation in the months to come: international commodity prices (he meant oil) and the monsoon.

The oil and water that run the Indian economy come from beyond our boundaries. Draw a list of factors holding back the aspirations of New India; alongside not having any oil reserves of our own will rank a reliance on an unpredictable rainy season. Imagine the state of our economy if unrest in West Asia sends oil prices higher and the monsoon fails.

In business dailies and government documents, ‘dependence on the monsoon’ is often cited as a serious limitation, a malaise. It is as if Bharat cannot become India because of one of the world’s craziest seasonal cycles. Actually, it is the other way around. New India can learn a thing or two about planning for the monsoon from old India.

A good starting point for that is Anupam Mishra of the environment cell of Gandhi Peace Foundation. He has spent more than two decades researching India’s traditional water management. “All decisions on land use were based on drainage,” he says, “Boundaries between villages were determined by the direction in which water drained.” The most pleasant surprises he encountered were in the state that receives the least rainfall in India: Rajasthan. “People have more than 40 names to describe clouds there.”

Jaisalmer is the heart of dryness in the Thar Desert, with an annual average rainfall of only 15 cm. Yet, the city had a series of nine interconnected tanks, all of which were very unlikely to fill up in most years. They had been planned for that one odd year of good rainfall, when all the water would be collected and stored in those tanks to let it seep into the ground—for use during the long dry months. Each drop was anticipated, nurtured and planned for.

Drainage was equally critical to managing floods in India’s wettest regions. It is what allowed people in north Bihar to withstand the violent floods of the Kosi River, and to harness the floods—a lesson modern engineers disregarded, with disastrous consequences. Bihar’s flood-prone area has increased in direct relation to the increase in expenditure on flood control. IIT engineer Dinesh Kumar Mishra has spent most of his productive years studying floods in north Bihar, and he says they have become unmanageable due to modern engineering interventions that disregard drainage.

This is the lesson Mumbai learnt after 26 July 2005. It took about 1 metre of rainfall within a day for the city to rediscover that it was originally a set of seven islands, with some of it built over the Mithi River Delta. Each major city in India has reported flash floods or water logging in recent years. Bangalore, Chennai, Kolkata, Delhi, Surat, Ahmedabad… they all live the flood-drought cycle. The stormwater drains of almost all our cities are inadequate.

The East Kolkata Wetlands, which have acted like a sponge for Kolkata’s excessive rainfall, are being filled up and built over under real-estate pressure.

In 2002, an ongoing case in the Gujarat High Court showed that most of the 204 lakes Ahmedabad city had in 1960 had been encroached upon and built over.

All it will take is one extreme downpour to show how badly our urban drainage systems have been neglected. In one day, Kolkata and Ahmedabad could be forced to learn what Mumbai learnt in 2005. Or Delhi, or Bangalore…

The way out of our flood-drought cycle is to think of the monsoon as a resource, not a liability. This requires that we accept the monsoon’s primacy in our lives. Since it delivers almost all our water, and does so in just three months, we need to allocate land for this water to spread itself over and get absorbed. That has been the key to survival in this Subcontinent for millennia.

Across the world, cities are changing how they manage stormwater drains. Property owners who pave their land have to pay steeper property taxes and stormwater charges—because they send more water into drains.

It is about time Indian cities adopt the same approach to rainwater. The reason we do not is simple: our large cities coerce their water from faraway reservoirs by depriving other villages and towns. Because they do not see the water that pours down on them as a resource, they notice it only when it floods.

Science is telling us—loud and categorically—that our rains are changing. The question is: can we?

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Categories: Science, Water

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