Atascosa County, Tex., is underlain by water-bearing sands of Tertiary age that furnish water for domestic and stock supplies throughout the county, for the public supply of all except one of the towns and cities in the county, for irrigation in several localities, for drilling oil wells in the central and southern parts of the county, for washing glass sand in the northern part of the county, and for maintaining several lakes that are used for hunting and fishing. By far the most productive formation is the Carrizo sand, but supplies of considerable magnitude are also obtained from sands in the Mount Selman and Cook Mountain. formations. The rate of withdrawal from the Carrizo sand amounted to about 15,500 acre-feet a year in 1944-45 or an average of about 13.8 million gallons a day. This was about 6,000 acre-feet a year greater in 1944-45 than it was in 1929-30. Of the total amount of water withdrawn in 1944-45 about 6,500 acre-feet a year is largely wasted from uncontrolled flowing wells. If the waste of water from wells in the Carrizo sand were stopped, the consumption of water for useful purposes could be increased about 70 percent without increasing the draft on the underground reservoir.
The increase in total withdrawals from the Carrizo sand has been accompanied by a general decline in the artesian head between 1929-30 and 1944 ranging from 3 to 25 feet. On the whole, the evidence shows that the artesian reservoir is not being overdrawn and that it will sustain a somewhat greater draft.