After quietly practicing a special skill for 40 years, Marc Mondavi has finally made it public. In addition to being a well-known vintner, he is a water witch (also known as a dowser or water diviner).

Mondavi has used his ability to locate underground sources of water to help establish vineyards for his family and friends all over California. It’s a valuable skill, particularly as water becomes more scarce throughout California.

Water divining, also called witching or dowsing, is a craft whose origins are as mysterious as the practice itself. It traces its modern roots back to Europe in the 1500s, but Herodotus the Greek mentions the craft in the fifth century B.C.

It has commonly been used to find underground water, but it has also been employed to locate precious metals, gems, oil and other materials or objects. Although skeptics abound, there’s abundant evidence to support it.

“I have been water witching since I was just a teenager,” Mondavi said. “It usually catches people a bit off guard the first time they see it, but my track record speaks for itself; I’ve been able to find water where geologists have come up dry.”

Mondavi is the eldest son of Peter and Blanche Mondavi and grandson of Cesare and Rosa Mondavi, who bought Charles Krug winery in 1943. He was born in 1954 and raised on the winery property. Growing up on a winery meant summers working in the vineyards and cellar, learning the wine business from the bottom up. He studied viticulture and enology at UC Davis, and marketing at California State University, Sacramento. He returned to the family wine business in 1978.

Mondavi worked with his father to further his knowledge of winemaking, and applied the expertise he acquired at UC Davis to the family’s numerous vineyard holdings. In the mid-’70s, he experimented with canopy management in the vineyards, which greatly reduced losses from mildew and facilitated grape ripening.

He also found water for the vineyards.

Mondavi discovered that he could find water underground when he was 17. He started working with the late diviner and grapegrower Frank (Laurie) Wood when he was 22. “He taught me most of what I know, though I learned some from trial and error,” he said. Mondavi worked with Woods for 15 years.

Mondavi continues to spend much of his time in the vineyards where he oversees the family’s vineyards across Northern California and ensures they remain properly irrigated. He has kept careful logs of his dowsing, and compares his findings with later results when wells are dug.

The most commonly pictured tools for diving are Y-shaped tree branches from willow, hazel or birch trees or fruit trees like apple, cherry or peach. The user holds the short ends of the top of the “Y” and points the longer base forward. A positive response to water involves the long end bending toward the ground to indicate location.

Another common divining instrument is the pendulum. Suspended in one hand, a pendulum can give similar positive and negative responses and indicate position.

Mondavi, however, uses two L-shaped brass rods, holding them parallel. They cross over sites containing water, and he says that he can instruct the rods to tell him the direction of flow.

In the past, he dowsed for relatives and friends, but now he does it commercially, too, taking on about one job per month.

Enjoy food? Get dining and recipe ideas sent to your inbox

In a recent day, Mondavi dowsed for grower Rick Jones, who has drilled nine wells, only to find four dry and two that went dry. The remaining wells provide only about 5 to 7 gallons per minute, but Mondavi found two locations at 700 feet, which he thinks would provide 18 to 20 gallons per minute. Mondavi says a house needs about 10 gallons per minute, and a vineyard on Howell mountain irrigated four times a year might need 70,000 gallons per acre each year.

Mondavi lives on Howell Mountain in the Napa Valley with his wife, Janice. They have four daughters: Angelina who got her master’s degree in enology from the University of Adelaide in South Australia; Riana, who is working as northwest sales manager for C. Mondavi & Family; Alycia, who is working as a marketing associate for C. Mondavi & Family; and Giovanna who is attending Northeastern University.

Marc Mondavi said that about half the population has the gift to find water. He has prepared a booklet, “Turning Water into Wine,” for potential dowsers. He also has written a pop-up book for adults about his talent, and posts information on Facebook under The Divining Rod.

Divining Rod Wines

Marc Mondavi recently launched Divining Rod Wines through C. Mondavi and Sons. The current releases are a 2010 chardonnay and a 2010 cabernet sauvignon. The chardonnay comes from well-regarded Santa Lucia Highlands of Monterey County, and the cabernet comes from Alexander Valley of Sonoma County. Each bottle contains some wine made from grapes grown on vineyards where Mondavi witched a well.

“The Alexander Valley Cab is softer than Napa Valley cabs — and less expensive,” said, Mondavi adding that plans are to add another variety to the duo.

Both retail for approximately $17 and are available nationwide. Production was about 20,000 last year.