Indian cities are running out of water. 11 of IndiaÕs 20 largest cities face ÔextremeÕ water stress, while seven others face ÔhighÕ stress At least half the urban water supplies in India are through groundwater, and IndiaÕs urban groundwater resources are severely overdrawn. A groundwater availability assessment study conducted by Central Ground Water Board of India in 2017 shows that out of the 10 most populous cities in India, the groundwater resources in 50% were over-exploited; 30% had critically low levels. Climate change will only make this situation worse. For every 1¡C of warming, another 7% of the population will experience water scarcity. The question is how? Most Indian river basins are ÒclosedÓ basins; all of the freshwater is already allocated. The opportunity The deficit will have to come from wastewater reclamation. 80% of water returns as wastewater but two thirds of IndiaÕs wastewater is not treated. If wastewater could be treated to standard and banked for aquifer storage and recovery then groundwater depletion could be reversed. There is an opportunity because decentralised, private wastewater systems are being promoted, even mandated by governments to manage the waste and sewage problem.