When it comes to rain water harvesting, Tamil Nadu leads by example.

In 2003, the state passed an ordinance to install rain water harvesting structures in all old and new buildings.  Now people in the state are reaping rich benefits. The ground water table in the state has shown a phenomenal rise.

Forty percent of rainwater which would earlier flow into the sea is now being stored underground.

In Chennai alone, it's like a whopping 150 sq km underground reservoir. As a result of this, water scarcity is now a thing of the past.

"Even during the worst crisis period, I had four feet of water in my well," says Chennai resident Hariharan, whose house has turned a lot greener, thanks to rainwater harvesting. He has a simple system that collects rainwater from the rooftop and ground surface and lets it collect in a percolation pit.

"Now we are never without water. We don't have to run to the well to see if there's water. We have plentiful supply," said V Ramaswamy, also a resident of the city.  

In the drought-prone Virudhunagar district also, residents have a network of pipelines connected their rooftops.  

Rainwater harvesting has become a people's movement in the state. When Jayalalithaa made this compulsory, many were skeptical. Today even her critics call this a revolution in conservation of water, worth replicating across the country.