Award-winning science writer Nancy Castaldo traveled across the United States and to other countries to research communities having a water crisis. The result is "When the World Runs Dry: Earth's Water in Crisis." 

Castaldo takes readers from Flint, Michigan, and Newark, New Jersey, to Iran and Cape Town, South Africa, to explore the various ways in which water around the world is in danger, why we must act now, and why you’re never too young to make a difference.