TEJA KA BAS, India — Bhanwar Lal Yadav, once a cultivator of cucumber and wheat, has all but given up growing food. No more suffering through drought and the scourge of antelope that would destroy what little would survive on his fields.

Today he has reinvented himself as a vendor of what counts here as the most precious of commodities: the water under his land.

Each year he bores ever deeper. His well now reaches 130 feet down. Four times a day he starts up his electric pumps. The water that gurgles up, he sells to the local government — 13,000 gallons a day. What is left, he sells to thirsty neighbors. He reaps handsomely, and he plans to continue for as long as it lasts.

“However long it runs, it runs,” he said. “We know we will all be ultimately doomed.”

Mr. Yadav’s words could well prove prophetic for his country. Efforts like his — multiplied by some 19 million wells nationwide — have helped India deplete its groundwater at an alarming pace over the last few decades.