Dowsing has in fact not been proven to work. There is instead overwhelming evidence that it does not work better than chance.

Wikipedia sums it up nicely, with citations: -- The motion of such dowsing devices is generally attributed to the ideomotor phenomenon,[7][8][9] a psychological response where a subject makes motions unconsciously. Put simply, dowsing rods respond to the user's accidental or involuntary movements.

The scientific evidence is that dowsing is no more effective than random chance.[10][11] It is therefore regarded as a pseudoscience. -- https://en.m.wikipedia.org/wiki/Dowsing

For an entertaining time, check out the late James Randi and his debunking of dowsing