Public water supplies in southern Texas

Abstract

This report gives a summarized description of the public water supplies in 42 counties of southern Texas, extending from the Rio Grande northward to the northern boundaries of Kinney, Uvalde, Bandera, Kendall, and Hays Counties and eastward to the eastern boundaries of Caldwell, Gonzales, DeWitt, Victoria, and Calhoun Counties. It gives the available data as follows for each of the 114 communities: Population of the community; name of the official from whom the information was obtained; ownership of water works, whether private or municipal; source of supply, whether ground or surface water; the amount of water consumed; the facilities for storage; the number of customers served; the character of the chemical and sanitary treatment, if any; and chemical analyses of the water. Where ground water is used, the following information also is given: Records of wells, including drillers' logs; character of the pumping equipment; yield of the wells and records of water levels, where they are available. The communities served by these public supplies had a population of 668,000 in 1940. Ground water is used by 79 of these communities and surface water by 31, The total amount of water consumed averages about 95 million gallons a day, of which about 55 million gallons is obtained from ground water and about 40 million gallons from surface water. The extreme northern part of the region lies on the Edwards Plateau, and the remainder lies within the Gulf Coastal Plain. The rocks that crop out in the region are practically all sedimentary and consist chiefly of limestone, shale, clay, sandstone, sand, and gravel. They range in geologic age from Lower Cretaceous to Quaternary. The general geologic structure of the region is comparatively simple. The most prominent features are the regional gulfward dip of the formations at an angle greater than the slope of the land surface, which is a significant factor governing the ocurrence of artesian water, and faulting along the Balcones fault zone which controls the occurrence and movement of ground water in the Edwards and associated limestones. Among the most important aquifers are the Edwards limestone of Lower Cretaceous age; the Carrizo sand, sands of the Mount Selman formation, the Oakville sandstone, and the Goliad sand of Tertiary age; and the Lissie formation and sands of the Beaumont clay of Quaternary age. Each of these units has outcrop areas from which the beds dip beneath younger formations to increasingly greater depths. For convenience in summarizing the sources of municipal water supplies, the region has been divided into four areas, as shown on plate 1. In area A, Bandera obtains its water from sands in the Trinity group; Divine in southeastern Medina