The geologic formations from which the Houston district obtains its water supply are upper Miocene, Pliocene, and Pleistocene in age. These formations are continental in origin and consist of interbedded sand, clay, and gravel. The section has been subdivided into seven zones by electrical logs. The annual pumpage in the Houston and Pasadena areas was nearly constant from 1930 to 1936 but increased about 60 per cent between 1937 and 1941. From 1930 to 1936 the water levels were in approximate equilibrium. The large increase in pumpage caused a marked decline in the water levels. In the Katy area the annual pumpage decreased somewhat from 1930 to 1935, but increased more than three-fold from 1935 to 1940. There has been a net decline in water levels over several years. The quality of the ground water used in the district compares favorably with other supplies in the United States. Data from exploratory drilling show that an additional supply of ground water is available west and north of Houston, and that salt-water encroachment from down the dip is not likely to occur for at least many years.