The city of 1000 tanks: a game-changing approach to address sewage overflow, floods and droughts

The Water Balance Pilot project is an initiative of Henk Ovink, the Netherlands’ first Special Envoy for International Water Affairs. It is funded by Partners for Water, in partnership with the city of Chennai, UN-Habitat and Resilience Cities Network and supported by the UN High-level Panel on water, amongst others.

Blueprint for the city

The project serves as a model for how a city can become water-secure using Nature-based Solutions. It harvests rainwater and treats wastewater before recharging into the underground aquifer through infiltration gardens. Eva Pfannes, Director of Ooze Architects and Urbanists and team leader of City of 1000 Tanks shared details about the project: “The Water Balance Pilot project is the  first example that will reach its full potential when replicated in institutions across the city. In parallel, we plan to scale it up through a flagship project in Mylapore.”

Partners for Water

Partners for Water is honoured to make the Water Balance Pilot project financially possible. The objectives of the Partners for Water programme are to encourage knowledge sharing, innovation and an integrated approach. Through these efforts, we strive to contribute to the expansion of sustainable solutions that enhance water security. The City of 1000 Tanks seamlessly exemplifies these principles. The pilot initiative has gathered valuable knowledge and experience that can be harnessed in scaling up this innovative solution across various parts of the city and potentially beyond.

Dual-aquifer recharge wells

Generated by the 300 residents, the Water Balance Pilot project collects 27,000 litres of wastewater per day which is then treated in two stages: the first stage is where two underground anaerobic tanks, rich with microorganisms, work on the pollutants to achieve 80% of the treatment capacity and the following stage is where the water is then allowed to flow through created wetlands with helophytic plants enabling aerobic treatment. No toxic chemicals are used and the project is completely supported by solar power. Bad odours and mosquito breeding are also eliminated.

The treated water is then released to the ground through infiltration gardens. This minimum-maintenance project is equipped to harvest rainwater during Chennai’s short and intense monsoons. Dual-aquifer recharge wells collect, store, filter and finally recharge rainwater to the shallow and deep aquifers.

What is next?

To scale-up the Water Balance project to other parts of the city, the City of 1000 Tanks-team aims to involve the government such as the Chennai Metropolitan Water Supply and Sewerage Board and the Greater Chennai Corporation for the greater good. In order to make Chennai water secure, they also welcome the participation from resident welfare associations, vulnerable communities, CSR partnerships and institutions.