The collapse of this system over the years, experts say, has contributed to Chennai's water crisis.
One of the reasons for the unprecedented water scarcity in Chennai, experts say, is the collapse of the rainwater harvest system, which was quite efficient till about 15 years ago.
To make things worse, there's very little scope for rainwater to percolate into the ground as Chennai has become a denser concrete jungle over the years.
At Chennai's Mylapore Ambujam, a local oversees repair of her apartment's nearly a-decade-and-a-half-year-old rainwater harvest system.
The rainwater harvest system at this apartment was not cleaned for a decade and now hardly any water which is collected from the terrace gets percolated into the ground. Half a dozen workers dig a new recharge well at the apartment's entrance to draw rainwater that would normally flow to the road and find its way to the sea through the storm water drains.
That's the case with thousands of homes across the city facing an unprecedented drinking water scarcity after authorities had cut piped water supply by about 40 per cent last month.
16 years ago, the Jayalalithaa government had made it mandatory for buildings across the state to have rainwater harvest system. The aquifers or the permeable rocks, which can contain or transmit groundwater, gradually rose by four meters, according to rough estimates.
However, poor enforcement by the Chennai Metropolitan Development Authority and lack of maintenance by property owners meant that rainwater harvest structures were set up in the houses only to comply with norms.
The collapse of this system over the years, experts say, has contributed to Chennai's water crisis.
Dr Sekhar Raghavan, Director of the Rain Centre, which has been working for the cause of rainwater harvesting for close to two decades, says: "They (locals) just did something to comply with the law. That's a big mistake. Secondly, these structures have to be maintained but nothing like that was done. When governments change such policies also take a back seat."
He also points out the storm water drains, along hundreds of kilometer-long roads and streets in the city, do more harm by indiscriminately dumping water into the sea to prevent inundation. "This is the worst thing to happen. These take all the precious rainwater and dump it into the sea. Particularly in coastal cities like Chennai, storm water drains are an anti-harvest measure," he explained.
A new threat is emerging in the state capital from the growing trend of paving or completely sealing the open around houses, apartment complexes and commercial properties with cement so that these spaces can double up as driveways for cars and vehicles parked there.
Experts point out though parched Chennai received 19 cm rain over the last three weeks, much of it could not be saved. While the rain was harvested from rooftops, the water that fell in open went down the drain into the sea with city roads and pavements leaving little room for percolation.