While there are some successful dowsing outcomes, there are untold numbers of failures. Untold because no one bothers to talk about all the times dowsing didn't work. In reality, it works as well as chance will allow. No better, no worse.
In looking for groundwater, chances are extremely high because groundwater is broadly distributed, not flowing in underground streams as dowsers believe. True story: when my ex-father-in-law was a kid his father bought a farm. They needed a well and a neighbor offered to dowse the best spot, which he did. When the well driller showed up he asked, "Where do you want the well?" The farmer said, "I was told it needed to be way over there." The well driller said, "I can put it there, or I can put it close to the house where it will be more convenient." He drilled the well close to the house and got excellent yield. Such is the case with groundwater.
With buried wires and pipes, GoDeep correctly surmises that people experienced with buried utilities can very often eyeball the locations withing a few feet. And dowsing rods are often used to bolster their confidence. Good chances, but it doesn't always work. True story: as a teenager I worked for an irrigation company, mostly installing nurseries and golf courses. I saw numerous times where the guys would pull out dowsing rods to locate pipes that they themselves had laid in the past. I was not impressed. One day we were on a golf course trying to locate where a main came out of the pump house. The owner of the company grabbed some dowsing rods and started at the pump house (where you could see the pipe enter the ground) and dowsed its path out to the fairway. I was the monkey with the shovel and dug where he told me to dig. No pipe. Over & over, no pipe. Then the company welder showed up and said, "Oh no, the main goes in the opposite direction, through those pine trees, to the other fairway." Completely opposite to what was intuitive.
Which is what dowsing is: Intuition and Luck. Treasure hunters can also eyeball hunt locations and intuit the best places to focus on. Dowsing rods simply indicate their subconscious selections. This explains why, in scientific testing, dowsing fails to work. A good test is designed to eliminate intuition and predict luck. I have studied dowsing and dowsers and, by extension, LRLs for over 20 years. I've personally tested quite a few who absolutely swore they "could do it" yet, when I was watching, they could not. It's been 20+ years of exactly the same outcome. There's no need to cheat to make a dowser fail (reference to the Randi comment), all you need is a good scientific test protocol. They will fail on their own because the hard reality is, dowsing doesn't really work.
For those who think they can do it and really want to know whether it's truth or illusion, I will gladly offer to help with that. For those who think they can do it and don't care whether it's truth or illusion, there's nothing more to discuss.