In many parts of the world, there are simply no more conventional freshwater resources available to meet growing demand. Beyond limiting economic development, the lack of sufficient freshwater resources threatens the wellbeing of billions of people by causing conflict, social unrest, and migration. The only way to address this challenge is by radically rethinking water-resource planning and management in a way that emphasizes the creative exploitation of unconventional water sources. By Manzoor Qadir and Vladimir Smakhtin