Thames Water and Severn Trent Water still use dowsing rods to hunt for leaks, even though scientific studies show that they do not work.
Water dowsing, also known as water divining which dates back to at least the 16th century, involves a person holding two L-shaped or one Y-shaped rod in front of them. The rods, sometimes known as witching sticks or wands, are supposed to twitch or cross to indicate the presence of water underground.
There is no known force in physics that would account for how buried water would move the rods, and scientific trials have shown that dowsing is no more effective than guessing.
Experts have asked Ofwat, the water regulator, to stop companies spending money on it. Thames Water, which supplies 2.6 billion litres a day, has admitted that about a quarter, or 650 million litres, is lost in leaks. Severn Trent loses about 400 million litres a day. Last year’s official declarations of drought focused attention on the poor state of water infrastructure.
The two companies told New Scientist that their engineers used dowsing rods to find leaks; 15 water companies told the magazine they had abandoned the method. A spokesman for Thames Water said dowsing rods were used to find leaks, and to verify results from other equipment. “Some people they work for, some people they don’t. If they work for you, you come to trust it,” he said. “People are sceptical of it, and I was sceptical when I first saw it. I started using them because I saw someone else use them and I have found leaks.”
Severn Trent said that a small number of its “expert engineers . . . may still carry dowsing rods with their equipment.” However, it added that it did not issue them as it did not consider dowsing rods to be effective.
Experts have attributed belief in dowsing to confirmation bias: the tendency to forget times when the method failed and celebrate it when it appears to work.
Professor Richard Wiseman, a psychologist at the University of Hertfordshire, said that it was plausible that some dowsers picked up on signs from the environment, such as green patches of vegetation, to be led to water sources. “I’m not sure that there’s any evidence that this happens, but it doesn’t seem impossible,” he said.
“In studies where there are no environmental cues, it fails.” he added.
Something known as the ideomotor effect may also play a part in the phenomenon of dowsing. This happens when somebody moves without meaning to and might explain why divining rods seem to twitch and move of their own accord.
The use of water dowsing by water companies made the headlines in 2017 when a couple in Warwickshire called out engineers from Severn Trent and were surprised to see them “walking around holding two bent tent pegs to locate a pipe” near their home in Stratford-upon-Avon. They told their daughter Sally Le Page, who was a scientist at the University of Oxford.
Ten of the big 12 water companies in Britain told her at the time that they were still using the technique. She described them as trying to “use magic to do their jobs”.
www.thetimes.co.uk
