lol . . not sure this is how they do it
I analyze wells from many states. In each case the state decides where to drill, I think, if not the EPA. Sometimes industrial waste gets into the groundwater and we have to test on private land nearby . . . for decades if not centuries.
Yeah, that's just it. Even if witching worked, how would you know if you'd found a safe and sustainable source? In other words ,if water was close enough to the surface to be detected by witching, there's a pretty good chance it would actually be contaminated surface water that's formed a pseudo aquafer, rather than true groundwater.