is there a instrument used to detect under ground water using capacitance principle
welcome to PF
dunno, I have never seen one
but I can do it with a "L" shaped length of copper wire :)
Have you considered using Google to find some answers? I searched with "water level measurement capacitance" and was totally flooded (no pun intended) with hits at all levels of technical complexity. Perhaps you should find some of these and then start a less 'open ended' discussion about their relative merits.
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