ORANGE COVE, Calif. — Standing in the middle of a 400-acre ranch, Rob Thompson pulled out two L-shaped steel rods and held them perpendicular to the ground.

“I’m grounding,” he said. “It’s kind of like rebooting the computer.”

Thompson then lifted them up and began rotating in a circle, waiting for them to cross.

“See that? Now that’s a keeper,” he said.

Thompson is a water witch who says he can find underground reservoirs and even pinpoint how far down to drill.

“To me, it’s like magnetism,” he said. “It’s like the energy between two magnets when they just pull you together.”

Water witching, also known as dowsing or divining, dates back to the Middle Ages. The American Society of Dowsers says it has about 2,000 members, many of them are working water witches. And while there is no science to back it up, it hasn’t stopped many of California’s top farmers and wineries from shelling out big bucks for their services.

“Some people scratch their heads. A lot of people laugh at me. It’s funny until they call me,” Thompson said.

Thompson charges $1,500 for the first two hours and another $650 for each additional hour. While that’s no chump change, it’s still a fraction of what it would cost to hire a hydrogeologist.

So far, this has been Thompson’s busiest year yet, as California faces a crippling drought that has left its water reservoirs depleted.

On a cloudy February morning, Thompson arrived at a plum ranch about 30 minutes South East of Fresno, where water has reached dangerously low levels.

Mike Medders, the ranch manager, said finding water was crucial, adding the ranch would be forced to make some “hard choices” if Thompson wasn’t able to locate underground wells. He admitted to being a bit skeptical about water witches at first. But a few years ago, someone had suggested hiring a one, and he decided to give it a try.

“He marked 17 wells for us, and 15 of them are still running today, so [he] made a believer out of me,” said Medders.

By the end of the day, Thompson identified 12 potential reservoirs, which he believes contain anywhere from 400 to 600 gallons per minute.

The ranch said it planned on drilling in those locations in about a month. If Thompson turns out to be right, it could triple their water supply.

Thompson said he wasn’t too worried, adding his success rate was at above 90%.

“There’s always the skeptics,” he said. “But it’s fun to prove them wrong.”