Open wells under parking spaces: Chennai's quiet groundwater revolution

For many apartment residents in Chennai, the open well might seem like a relic from a bygone era — a structure with a parapet wall, a pulley and a bucket. With space at a premium, keeping one may appear impractical. But an open well does not necessarily mean sacrificing a parking spot or valuable open space. With the right design, it can be built below ground, allowing vehicles to pass over it while the well continues to collect rainwater and recharge groundwater.

This is exactly what N. Ramshankar, an executive member of The Rain Centre in Adyar, has demonstrated. An old open well on the premises that once held only about two feet of water now retains around 16 feet, after rooftop rainwater was directed into it with minimal filtration. The well is now covered with a slab at floor level, and vehicles drive over it without any visible trace.

Sekhar Raghavan, director of The Rain Centre, explains the practicality of such designs. “Unless I open the lid, you will not even know that there is an open well below,” he says. These wells can be incorporated into driveways or parking areas, provided they are kept away from structural columns. “You can have your open well within your stilt car parking,” says Sekhar. The minimum diameter required is about 3.25 feet.

Initially, there were concerns about safety and gas accumulation. Ramshankar recalls, “We were afraid in the initial days. We were wondering whether an open well can be closed and whether it will accumulate gas and all that. An engineer told us, ‘Don’t make that mistake, nothing will happen.’ He even set up a vent for us.” The parapet wall was later demolished, and a concrete slab was placed at floor level. Now, vehicles pass over it routinely.

The benefits extend beyond saving space. The quality of water has improved significantly. “The TDS has also been diluted from almost 850 to now 400,” says Ramshankar. This improvement is due to the influx of rainwater, which replenishes the shallow aquifer and dilutes dissolved salts.

Open wells tap the shallow aquifer, typically 25 to 30 feet below ground, and at most about 40 feet. Unlike deeper hard-rock aquifers tapped by borewells, this shallow groundwater can be replenished more easily through rainwater harvesting. By directing rooftop rainwater into an existing well, residents not only recharge the groundwater but also improve its quality.

Sekhar Raghavan advises a strategic approach: “During monsoon, your open well will have a lot of water, and a couple of months thereafter. So, start tapping it. Then during summer months, go to your borewell.” For apartment complexes, this can translate into a significant reduction in dependence on tanker water.

At Hiranya Apartments in Raja Annamalaipuram, resident Raghunandan Ranganathan says the open well was never shut, even though three borewells had been installed and two were later closed. “This open well is what is giving us a lot of water,” he says. The apartment had rainwater-harvesting infrastructure, including percolation wells. But during heavy rain, water would collect in the compound and flow out through the gates. The residents then sought Sekhar Raghavan's help.

“We made collection pits at every gate and diverted the water to the percolation pits, which in turn were feeding the well,” says Raghunandan. Over time, this system improved both the availability and quality of water in the apartment. He laments that builders often ignore existing open wells: “Builders often do not make use of the open wells available on a property. Instead, they tend to shut them down and install borewells. I am not able to understand the logic behind this.”

At Bayview Apartments in Besant Nagar, the open well has been in use since the building was constructed around 1989-90. Resident K. Sangameshwar says, “We are using an open well. Generally, during the rain, mainly after the Northeast Monsoon, it fills up.” The apartment also has two borewells, but the open well provides a reliable supplement, especially during the post-monsoon months.

This revival of open wells in urban Chennai offers a practical solution to groundwater depletion and water scarcity. By creatively integrating these traditional structures into modern designs, residents are demonstrating that water conservation and urban convenience need not be at odds. The approach not only saves space but also builds resilience against seasonal water shortages, reducing the reliance on external water supplies.

As cities across India grapple with groundwater stress, the example set by these Chennai apartments provides a replicable model. With proper engineering and community participation, open wells can serve as sustainable water sources for generations to come.