Apparently dowsing is still used in California's Central Valley to determine where to drill wells (the valley sits on top of an aquifer, though it is being drawn down unsustainably).

I asked a farmer about this and he said that yes, he uses a "witcher" and that they are good at finding water though they can't tell you how deep (!!). Of course I assumed he was pulling my leg but I later encountered someone on that property wielding a coat hanger to tell this same farmer where to drill.