This is a trick question. So which is the month that receives the highest rainfall in the year in Bangalore? The typical answer would be June or July in these parts of what the weatherman calls south interior Karnataka. Well, for over 30 years the rainfall pattern has shown that September recorded the highest rainfall! So which is the second highest rainfall month in our parts? That again will surprise you. May happens to be the month that records the second highest rainfall in a year. This year showed April to be a month which received more than it usually does, but by and large the rainfall pattern has held for many years to be the same.
So what does this pattern depend on? The Indian subcontinent is the only region in the entire world which is dependent on winds that flow 24/7 from across the seas into the land and back again into the waters of the Arabian Sea, the Bay of Bengal, and the vast Indian Ocean that lies beneath.
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The northeast and the southwest monsoons are as old as Time in a sense and travel at a speed of 12 to 18 km an hour. But these winds must have shifted and taken these directions ‘very recently' when the Himalayas were formed — just over 15-20 million years ago. This is a flash in geological spans of time considering that the earth goes back to over 4,000 million years.
When the southwest monsoon hits Kerala around June 6, the winds rush to meet the depression that is formed over the great Indian plains, especially to the heart of India. In Balharshah or Nagpur, the temperature soars at 45-48 degree centigrade when the monsoon winds hit the mainland at the western coast. These winds travel right across, searching the sub-Himalayan wall toward the northeast. This travel of the winds, across from the west coast toward north Karnataka and past into the central parts of Andhra and into Bengal and beyond, takes about 40-50 days. And then when these winds hit the Himalayan wall, they turn around and move east toward the Gangetic Plain. Now the winds gather speed, lured by the heat and stillness in the air in the great plains.
Poets for centuries in the Hindi heartland have called these rain-bearing, cooling winds the Puruvaiya because, for them, it has been the ‘easterly' winds. By the time the monsoon hits Delhi it is July 15 as we are seeing just now with those reports of floods in Haryana and Punjab. The winds lose their steam as they hit the Aravalli to the east of Rajasthan, and southwest of Delhi. This hilly belt stretches 600 kilometres on a north-south traverse and so blocks the winds and sends them back all over again. And so the return journey begins by the end of August all the way down to the Gangetic Plain, until the great Himalayan barrier steers the winds back south. These winds gather force once again as a depression forms in the Bay of Bengal, drawing these winds towards the southern peninsula. By this time we are into the end September. And so the returning monsoon or the northeast monsoon hits the east coast around October.
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What is interesting is that nearly 75 per cent of India's landmass receives about one meter of annual rainfall. The parts that unfortunately rely on the lee side of the hills that crisscross India's lands are the ones which suffer rainfalls less than 400 mm. The lands behind the Aravallis, which fall in parts of western Rajasthan or northern Gujarat, get under 100 mm rainfall. The same goes for certain parts of north Karnataka, for instance. An entire culture of water consciousness with vavs (or crafted open wells) in Gujarat and complex tank architecture in north Karnataka have evolved over 5,000 years of such low rains.
Totally dependent
Our lives in India are so fragile and vulnerably dependent on the monsoon winds. A deflection of even four degrees in the travel of these winds in any particular year can make for drought in several districts. To this day, with all the economic and technological advancements, the irony is that farmers continue to look up to the sky and pray for the winds and the rains to be right on time; urban citizens, in their search for solutions for water and power shortages, are as completely dependent on the monsoon for life and living. If the farmer can't grow food without the winds and the rains, the urban dweller does not get power at home, and food at the kirana store or mall, without the rich water catchments that either generate hydel power or increase the inflow of greens and cereals into the market.
As we go about the bustle and din of our city lives, we don't realise how deeply connected we are in this bigger picture. We remain often oblivious to these enormous forces that determine so many things in our lives; forces that will remain much after we have passed and, well, even after our present civilisation has passed.
The writer is a conservationist based in Bangalore.