A weak monsoon and years of draining groundwater have parched Chennai, a city of nearly five million people on the southeastern coast of India.

When the water's gone, you bathe in what drips out of the air conditioner. You no longer allow yourself the luxury of an evening shower at the end of a steamy summer's day. You sprint down two flights of stairs with plastic pots as soon as a neighbour tells you the water tanker is coming.

Every day, 15,000 tankers ferry water from the countryside into the city. Everywhere you look, rows of bright neon plastic water