Water-witch*: noun. One who claims to be able to find underground water by means of a divining rod; a dowser.
Finding reliable sources of freshwater is a problem that plagues the American West. People resort to a number of obscure methods for obtaining sources of subterranean water. New homesteaders in the American West might pay a water-witch a few dollars to find a reliable source of water. Although water-witches are often associated with the bygone homesteading days, it still persists in areas plagued by terrible droughts.
*Source: Free Dictionary (2014)