July 10, 2018 — Twenty-five years ago, Chennai, a city on the southeastern coast of India, could barely supply enough water to its 3.8 million citizens. Many of its families depended on water drawn into plastic pots from public stand pipes and pumps. There was not enough water to go around, and municipal supply was unpredictable, with the taps running only intermittently.
People who could afford to do so began to hire private water tankers. Others drilled deep boreholes that tapped discontinuous and unsustainable aquifers in the bedrock of the soil — over 60 meters (200 feet) under the surface. A very small proportion of the population had access to freshwater in subsurface aquifers close to ground level.
Today the population of Chennai has more than doubled. The city gets water from four large suburban reservoirs and two desalination plants. River-water sharing agreements with other states have augmented these sources. However, the city remains deeply dependent on groundwater.
Yet sidewalks are no longer clogged by plastic pots. Water tankers are a lot less common, and most of Chennai’s citizens have forgotten the days of surviving on less than 40 liters (8 gallons) of water a day. The city has managed to avoid a Day Zero scenario like the one Cape Town, South Africa has been facing. A lot of this improvement has come from a simple idea promoted by physicist and Chennai resident Sekhar Raghavan: Rainwater could quench the city’s thirst.