This story appears in the March 2019 issue of National Geographic magazine.

Northern India embraces a sprawling network of waters, from the muddy tributaries of the Indus in the west to the banks of the sacred Ganges coiling along its central plains and the miles-wide currents of the Brahmaputra in the east. Creeks, canals, wetlands, dams, and swollen torrents help irrigate the most populous democracy on Earth. Yet this river-etched heartland is the scene of one of the most dire water crises today.

Last year, a government study revealed that nearly half India’s population—some 600 million people—ekes by on scarce or polluted supplies of water. As many as 200,000 Indians die annually from the effects of water contamination. And it’s been projected that more than 20 major cities—Delhi, Bangalore, and Hyderabad among them—will zero out their groundwater stores in less than two years.

View Images The Out of Eden Walk National Geographic, and follow his odyssey online at outofedenwalk.org. In 2013 Paul Salopek began what he calls “an experiment in slow journalism,” a 21,000-mile storytelling walk along the pathways of the humans who first explored Earth in the Stone Age. As he travels, he’s covering the major stories of our time by giving voice to the people who inhabit them every day. Look for the account of his foot traverse across water-stressed northern India in an upcoming issue ofand follow his odyssey online at NGM Maps

I witnessed this slow-motion environmental calamity while walking hundreds of miles across rural landscapes visited by few outsiders. In the state of Madhya Pradesh, for example, I met a 12-year-old shepherd, Shailendra, watering his goats on the Chambal, one of several rivers the government hopes to “interlink” with other waterways in a drastic water redistribution plan.

In the lush Punjab, the pumps and pesticides of the green revolution have depleted precious reserves of groundwater and spawned hot spots of infertility and cancer. In the states of Rajasthan and Madhya Pradesh, villagers complained that fluoride—a mineral tainting new wells drilled for growing human populations—was discoloring their teeth and causing bone deformities.