With much of the American southwest in one of the most severe droughts in history, more and more people are turning to the ancient art of water dowsing. Dowsers-for-hire are seeing booming business, hired by farmers, winemakers, and others to help locate new sources of water.

According to an NBC News story, “The ancient method of discovering water underground is finding new life in drought-ridden states such as California.”

Dowsing, also known as rhabdomancy, is a process in which people use a forked branch, pendulum, two L-shaped wires, or other devices to search for hidden or missing objects.

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A forked twig is said to suddenly dip downward when over water, while a pendulum is said to swing a certain way, guiding the holder toward hidden water.

Though water dowsing is the best known type of dowsing, dowsers claim to find almost anything they search for, from missing persons to missing jewelry to deposits of oil and gold. Some dowsers even claim to be able to find things never proven to exist, such as ghosts.

Though the practice goes back many centuries, there is no scientific evidence that dowsing actually works. So why do so many people swear by it? The answer lies in statistics and psychology.

The first thing to understand about water dowsing is that dowsers are impressed at their success in finding something that is almost everywhere. Even during surface droughts, the hydrogeology in most parts of the world is such that if you dig deep enough you’ll find water in an underground aquifer just about anywhere.

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From a dowser’s perspective it’s easy to see why they claim success: Of course dowsers are convinced of their ability, since they often find water. No one can claim 100 percent accuracy — not even advanced geological analysis can do that. So the occasional wrong predictions are dismissed as normal human fallibility, while the successes are attributed to special water-finding abilities of the dowser or their equipment.

Dowsers and their clients aren’t thinking about water-finding from a statistical point of view; they are more interested in the seemingly mystical, supernatural powers exhibited by swinging pendulums and bobbing twigs.

There are thousands of sincere dowsers who proudly rattle off their success stories to friends, family, and potential clients. Science, however, proves its theories through repeated, well-designed scientifically controlled tests, not personal stories and anecdotes.

The question is not, “Can dowsers find water?” — for they (and anyone else) certainly can — but instead “Can dowsers find water with any better accuracy than random chance?”

A more challenging feat would be for dowsers to consistently locate places where water cannot be found; or to compare their water witching accuracy with a non-dowser who is just guessing; or even use a random-number generator to pick places to drill for water so there is some basis for comparison.

Dowsers have been scientifically tested many times over the years, and have performed no better than chance under controlled conditions. In 1986, for example, university physicists in Munich, Germany, received a $250,000 grant to conduct a large-scale study of water dowsing.

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In a review of the study published in Skeptical Inquirer science magazine, J.T. Enright, a professor of behavioral physiology at Scripps Institution of Oceanography, notes that “It is difficult to imagine a set of experimental results that would represent a more persuasive disproof of the ability of dowsers to do what they claim. The experiments thus can and should be considered a decisive failure by the dowsers.”

With some water dowsers charging hundreds of dollars in fees, landowners seeking water would do just as well to pick a convenient place to dig or drill and start there. They will probably find water, but even if they pay a dowser the worst-case scenario is wasted time and money.

A look at the history of dowsing reveals that centuries ago the consequences of bogus dowsing information was far more dire. In “The Book of Divination,” writer Ann Fiery notes that “Rhabdomancy was denounced as the work of the devil at various points in history, but it has been employed almost continuously in Europe since the Middle Ages… The French were… the chief innovators in its development as a policing tool.

In 1692, a peasant named Jacques Aymar used his divining rod to track down the murderers of a local wine merchant. His forked stick bobbed up and down dramatically at the murder site and then led Aymar through town, over the Rhone, and all the way up to Lyons, where he found a hunchback who confessed to taking part in the deed.”

This seems rather impressive, though Fiery neglects to mention that the hunchback, a boy of 19, “confessed” while being “broken on the wheel” — tortured to death by having his limbs broken and wrenched from his body. Despite the fact that a dowser likely implicated an innocent man based on no evidence at all other than a dipping dowsing stick, “Upon the publication of this detective story, judicial rhabdomancy became all the rage in France.”

Yes, there was a time in France when dowsing rods were used to decide a person’s innocence or guilt. While this was an extreme example, even today people put money and trust into mystical divination tools despite a lack of credible evidence they are valid.

Photo: A British farmer uses a hazel twig to attempt to find water on his land (1942).  Credit: Imperial War Museums.