The importance of ground‐water as a natural resource to be used for water‐supply and industrial purposes is often overlooked by the general public. A recent survey conducted by the Engineering News‐Record [see 1 of “References” at end of paper], based on data obtained from State Sanitary engineers, shows that 9,100 out of a total of 12,700 public water‐supply systems in the United States obtain water from underground sources. Of the total population served by public water‐supplies, about 28 per cent or 22,500,000 people are served by systems using ground‐water. In addition to the quantities of water pumped for public supplies, many million gallons of ground‐water are pumped daily for rural, domestic, and industrial purposes. In many of the cities that have public supplies from surface‐sources, there is nevertheless heavy pumping from private wells for industrial purposes.