Every Bengalurean knows the cycle by heart.

The first heavy showers break the summer, the gulmohars turn green overnight, and for a week or two the city almost earns its old title of Garden City. Then the rain stops being a relief. Roads vanish under brown water, basements fill, and a scooter commute that should take twenty minutes takes ninety.

Six months later, those same apartment complexes that were pumping water out of their basements are paying in five figures a month to have it trucked back in. Borewells cough and go dry. The resident WhatsApp group fills up with polite, then less polite, requests to go easy on the overhead tank.

How does one city drown and go thirsty in the same calendar year?

The answer is almost annoyingly simple. Bengaluru does not have a rainfall problem. It has a rainwater problem — the water arrives, and the city has arranged itself, street by paved street, to get rid of it as fast as possible.

The rain isn't the issue. Where it goes is.

Bengaluru receives roughly 970 to 1,000 mm of rain a year — comparable to cities that never run short. The catch, as the people who study this point out, is that it falls on about 60 to 70 days and then has to last for 365.

A R Shivakumar has spent three decades on that gap. A scientist at the Karnataka State Council for Science and Technology (KSCST) at the Indian Institute of Science, he is known around the city simply as Bengaluru's Rainman. AsThe Better India has reported, he has not paid a municipal water bill at his home since 1995 — the house, named Sourabha, runs almost entirely on rain he catches and stores himself.

When he was building it, Shivakumar did the arithmetic most of us never do. He pulled a hundred years of the city's rainfall records and found there was more than enough water even in the worst drought years; the problem was purely one of timing and storage. The gap between two good rains, he found, is seldom more than 90 to 100 days — so he built a set of rooftop tanks holding around 45,000 litres to ride out the dry stretch, positioned high enough that gravity did the work and no pump was needed.

His conclusion, from that earlier reporting, is the one worth pinning to the fridge: catch the rain wherever and whenever it falls, and if even half the city's homes were retrofitted with harvesting systems, Bengaluru might never face scarcity.

Instead, most of it runs off. As lakes, wetlands and open soil have been paved into roads, parking lots and slabs, rain that once soaked in now sheets across concrete and disappears down stormwater drains. By one widely cited estimate, the city lets around 23 TMC (thousand million cubic feet) of rainwater run to waste every year — water that instead overwhelms drains built for far less, which is a large part of why the low-lying neighbourhoods flood. The city's own water board, the BWSSB, reckons that harvesting even half the rain that falls on Bengaluru would yield 10 to 15 TMC of additional supply.

Subhajit Mukherjee, a water conservationist known as the "Water Hero of India" who has guided more than 200 households across the country on harvesting rain through his RWH India Helpline, puts the problem in a single line: the rain that falls on your roof shouldn't end up on the road. Every rooftop, he argues, should become a source of water rather than a feeder for the nearest drain........

© The Better India