“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.”