there are many, many anecdotal tales out there of water being found this way. In the mid 1950's my parents used such a person to find the spot to dig a well on land they owned.

Yes, I understand that anecdotes are not consered to add up to data, no matter how many anecdotes, but people tend to rely on their personal experiences.

As well as the dangers of relying on "personal experience."

" ... but when dowsing is exposed to scientific examination, it presents a very different picture. For instance, what does it mean to say that a dowser is successful in 8 out of 10 cases? The dowser may find water, but how much? And of what quality? At what rate can it be withdrawn? For how long and with what impact on other wells and on nearby streams?

The natural explanation of "successful" water dowsing is that in many areas water would be hard to miss.The dowser commonly implies that the spot indicated by the rod is the only one where water could be found, but this is not necessarily true. In a region of adequate rainfall and favorable geology, it is difficult not to drill and find water!

Some water exists under the Earth's surface almost everywhere. This explains why many dowsers appear to be successful. To locate ground water accurately, however, as to depth, quantity, and quality, a number of techniques must be used . Hydrologic, geologic, and geophysical knowledge is needed to determine the depths and extent of the different water-bearing strata and the quantity and quality of water found in each. The area must be thoroughly tested and studied to determine these facts. The U.S. Geological Survey, the Federal agency with major responsibility for assessing the quantity and quality of the Nation's surface and ground waters, believes that no single technique suffices to locate favorable water-well sites.

Numerous books and pamphlets have been written on the subject of water dowsing. Some of these publications report on scientifically controlled experiments and investigations. From these findings, the U.S. Geological Survey has concluded that the expense of further tests of water dowsing is not justified."


From: http://pubs.usgs.gov/gip/water_dowsing/pdf/water_dowsing.pdf

and personal experience.