Dowsing is among the most heavily tested practices in this atlas, because the claim is unusually easy to state and unusually easy to check: the dowser says water or metal is here rather than there, and one can go and look.
The general design is to conceal the target so that neither the dowser nor anyone present knows where it is, and to run enough trials to distinguish skill from chance. Under those conditions dowsers have not performed above chance in the published series. The most substantial programme was a large German study in which dowsers worked over concealed pipework in a barn; its authors reported that a few participants had done remarkably well, and a subsequent reanalysis of the same data concluded that the apparent successes were what a sample of that size would be expected to throw up by chance.
The rods do move, and the explanation is not in dispute among people who study it. Small unconscious muscular movements amplified by a finely balanced instrument produce motion the holder experiences as coming from outside, which is the same effect that drives a planchette and a pendulum. It is easily demonstrated by supporting the rods so the hand cannot influence them.
Dowsers commonly find water, and the reason is that in many landscapes water is widely present and an experienced person reads the ground, the vegetation and local knowledge without noticing that they are doing so.
The practice remains in use, and in some places has been criticised for being paid for from public funds.