The potentiometric surface is an imaginary surface representing the static head of ground water and defined by the levels to which ground water would rise in tightly cased wells. The potentiometric surface of the principal aquifer within the area of the Sugar House quadrangle ranges from about 20 feet above, to as much as 500 feet below land surface as is shown on the map. The principal aquifer supplied about 4 percent, or 9,000 acre-feet, of the municipal and industrial water used annually in Salt Lake County during 1964-68.