Rob Thompson and his dowsing skills are in high demand these days in drought-stricken Napa Valley, California - he is booked up to three or four weeks in advance. He locates water with two bent steel rods which cross when there is water underground, 'tuning in' to the presence of water as if finding a signal on a radio, and even indicating the depth at which water will be found. He has been doing it for 40 years. Vineyard manager Mark Neal, who has used Thompson's dowsing for 25 years, says he has never hit a dry well yet.