ABSTRACTGround water has emerged from a quantitatively minor (though incalculably valuable) source meeting widespread small‐scale needs to a source that is meeting a substantial percentage of the nation's total water demand and is capable of doing even more than it is. At the same time, many scientific, economic, legal, and managerial problems stand in the way of full development and must be solved if ground water is to make its maximum contribution to the nation's welfare.In recent decades ground water has accounted for something between one‐fifth and one‐sixth of the nation's total withdrawal use of water, which was about 170 billion gallons per day (bgd) in 1950, 240 bgd in 1955, and 270 bgd in 1960. As the total demand increases (estimates by the Senate Select Committee on National Water Resources, perhaps somewhat optimistic, call for 559 bgd in 1980 and 888 bgd in 2000), the fraction taken from the ground may go up or down or stay about the same, but the absolute withdrawal of ground water cannot help increasing. Furthermore, underground aquifers will play an increasingly important role as storage reservoirs for surplus surface water, through artificial recharge.Well drillers, as producers of both the ground water itself and much of the basic information needed for scientific prediction of the behavior of complex hydrologic systems, will play a key part in man's efforts to dominate his water problems before they dominat