Sandra Postel is director of the Global Water Policy Project and author of "Replenish: The Virtuous Cycle of Water and Prosperity." She is also co-creator of Change the Course, the national water stewardship initiative awarded the 2017 US Water Prize for restoring billions of gallons of water to depleted rivers and wetlands. For six years, she served as Freshwater Fellow of the National Geographic Society. Postel also wrote "Pillar of Sand: Can the Irrigation Miracle Last?" and "Last Oasis: Facing Water Scarcity," the basis for a PBS documentary. Her work has appeared in Science, Natural History and Best American Science and Nature Writing.