Several years ago, I took a journey with my wife and baby daughter to my mother-in-law’s childhood home, a forest village in the southwestern Indian state of Kerala. As any Keralite will tell you, Kerala is the lushest, most watery corner of India, a skinny coastal strip where hundreds of tributaries merge into broad, winding rivers before finally flowing into the Arabian Sea. My mother-in-law’s village is named Manimala, for the river that provides its reason for being. My wife spent her childhood summers in Manimala, and all her stories seemed to center on the river: the old stone steps that villagers descended to board a ferry or take a bath; the neighbors fishing or washing elephants; the flotillas of flowers that drifted downstream after monsoon gales. I’d been cultivating a fantasy that our own daughter would spend her summers on these banks. But when we arrived in Manimala, I was shocked: The great river had become a trickle. In a few places it had pooled into puddles big enough for people to wash their clothes. Otherwise it was barren, the stone steps now leading to a gouged-out ravine of pale boulders baking in the sun. What happened to the river? I asked. Sand mafia, my wife’s cousin Thambichan answered. The Manimala, Thambichan explained, once had a sandy riverbed that in some places was 30 feet deep. The sand acted as an aquifer, regulating the river’s flow. But sand is also a crucial ingredient in concrete, and India is urbanizing at a speed and scale virtually unmatched by any country in history. Apartment towers, highways, bridges, skyscrapers, metros, dams: Each of them swallows unimaginable helpings of sand. It could line the rivers, or it could form the cities that were rising everywhere alongside them, but it could not do both at once. No one listened when we warned of the dangers of sand mining, my wife’s uncle Shaji told me. With nearly all the sand removed from the river, the water table had dropped for miles around. When the monsoons came, the water whooshed away as quickly as the rain fell. The ordinary wells ran dry, so people drilled tube wells deep into the earth; now some of those were running dry, too. The local rice paddies were long gone. Along the river’s route, several major bridges faced collapse, because the loss of sand had weakened their foundations. When Indians use the term sand mafia, they’re talking about the whole range of people who profit from illegal sand mining: the local laborers; the budding capitalists who own the trucks and earthmovers; the genuine mobsters who, in some places, organize the miners and offer extra muscle; the suppliers who act as middlemen between the mafias and the real estate developers; the police and officials who take bribes from any or all of the above. And the politicians sometimes, it’s rumored, even chief ministers of major states who take their cut and maybe even run sand-mining operations of their own. The McKinsey Global Institute calculated that the hundreds of millions of Indians migrating from villages to cities require up to a billion square yards of new real estate development annually. Current construction, according to one estimate, already draws more than 800 million tons of sand every year, mostly from India’s waterways. Though no reliable numbers are available, all the people I spoke to in India assumed that much of it is taken illegally. As I came to know Manimala, it became clear that the river had mostly been mined by the villagers themselves. You could see the evidence in many of the new houses nestled among the rubber trees and coconut palms. Some were made of concrete, large and sprawling and brightly colored: pink, neon yellow, fire-engine red. A few had heaps of sand out front to be used for concrete or plastering for new wings and other renovations. One evening, I sat with Saji P. Thomas, a slender, energetic former sand miner with a small mustache, in front of his new house. He told me he started sand mining around 2002, to raise money for a new business. (He now runs a small cosmetics factory.) It was possible then to mine sand legally, but Thomas, like many others, didn’t bother with hard-to-obtain permits at first; he mined only at night to evade the police. They worked in groups of four or more, he said. Some would pilot the rowboat and the others would dive as deep as 15 feet to fill their baskets with sand. The loads were awkward and heavy. We’d make a staircase out of tree stumps, he said. But the danger was we’d slip off a step and almost choke to death underwater. At the river’s edge, another team would load the sand into a truck. Sometimes, Thomas said, the truck driver would get a call that the police were on their way, and they’d scramble to finish loading the truck and flee; any bribes the authorities might demand could cut deep into their margins. There are policemen who have built beautiful houses thanks to sand mining, he said. His previous job, at a bank, paid 400 rupees a day, roughly $5. A good night’s work mining sand earned him 2,000 rupees. So Thomas kept at it. To distract myself, I’d fantasize that I was a businessman in a nice car. The work did sound terribly dangerous. But the most striking detail in Thomas’s story was not about the mining itself, but about the attitude of his neighbors who lived at the river’s edge. Back when there was plenty of sand, trucks came day and night to load up at the river. But to get access they usually had to cut across the property of the town’s riverfront homeowners, most of whom would collect a toll of 150 rupees from each truck that passed. Now that sand mining has wiped out the groundwater, those same homeowners have to hire different trucks tankers to bring them drinking water, at more than 1,200 rupees a trip. The sand was gone, and gone with it were the river, the groundwater and even the tolls. All that was left was a question, one that haunts river communities all over India: Why would any village so willingly accept such paltry gains for certain catastrophe? More than half the apartments built during India’s construction boom can be found in the New Delhi metropolitan area. One of the highest concentrations of these apartments is in Greater Noida, a suburb that lies between the two most sacred rivers in Hindu lore: the Yamuna to the west, and the Ganges to the east. Both rivers are heavily mined, and it’s easy to see where all that sand goes.