I thought American water wizard Paul Polak was half-mad when I was chasing him around the Zambian countryside as he tried to bring cheap irrigation systems to small farmers. But Polak is an admirable character, and it was good fun trailing behind this dynamo. On the Kefue River he brought his road show to an impoverished village. Hundreds of people gathered as Polak demonstrated how a treadle pump—a cheap foot-operated, water pump—could irrigate their fields. As I and younger members of his staff wilted and headed for shade, Polak—drenched in sweat—continued to charge around, persuading villagers that small things like a pump could change their lives.

I spent a week in the Indian state of Gujarat, reporting on groundwater depletion in this dry, overpopulated region. Our schedule was full during the day, so we wound up driving from town to town at night. India’s roads are always jammed with cars, buses, trucks, people, cattle, and goats, but at night—when most of the truckers choose to work because it’s cooler—they’re even worse. The dust, pollution, heat, traffic noise and countless near accidents reminded me that I was a fool to have broken one of my rules of travel in the developing world—never drive on rural roads at night.

I came across numerous dried-up rivers on my trip, the biggest of which was the Sabarmati in Gujarat. It used to flow year-round and run through the heart of Ahmadabad, where I interviewed some of the 70,000 squatters who have taken up residence in the desiccated riverbed. They live in squalid shacks ten months a year and are chased out every summer as monsoon floods sweep away their semi-permanent town. After the floods carry off some of the shacks, the squatters return and set up camp again until the next monsoon.