Some years ago I was working on solar powered water pumps in California's Central Valley. The valley is irrigated by the California Aqueduct and also by groundwater (it sits on top of an aquifer).*

Turns out most of the farmers use "witchers" -- people with divining rods. Well, not all rods, some use a willow stick, yes, some use a wire coat hanger, and others, well, anything goes.

I asked one of these farmers -- a retired navy officer with a couple of graduate degrees how will it worked (his guy was the wire coat hanger guy). He said, "well, he can never tell me how deep to drill but when he finds a location there's invariably water."

* yes, they are pulling out water that flowed in 20,000 years ago faster than it's being replaced...and the dry parts collapse.