[SoundMan65]

My Gmaw had an old well we use to draw water from way back when when I was younger, the way we measured the water depth was to take ordinary cotton string and tie a weight to it, lower it into the well slowly until it stopped, pull it up and use a tape measure to check from the weight to where the wet area stopped, she had a 500 ft spool of string, It always worked for us, not scientific by any means but close enough. Hope it helps a bit.