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The average annual ground-water recharge to the Edwards aquifer in the San Antonio area, Texas, from 1934 through 1986 was 614,900 acre-feet. Recharge in 1986 was 1,153,700 acre-feet, which is the fifth highest estimated annual recharge since 1934. A maximum annual recharge of 1,711,200 acre-feet occurred in 1958, and a minimum annual recharge of 43,700 acre-feet occurred in 1956.

The calculated annual discharge by wells and springs in 1986 was 834,500 acre-feet. Annual discharge by wells and springs ranged from a maximum of 960,900 acre-feet in 1977 to a minimum of 388,800 acre-feet in 1955. In 1986, the annual discharge by wells was 429,300 acre-feet, which is below the midpoint between the record maximum and the record minimum.

In 1986, water levels in many of the wells fluctuated above the midpoint between record high and low levels; consequently, the volume of ground water in storage in the aquifer was above average during most of the year. In 1986, substantial recharge occurred during the summer, and water levels then remained above average in most of the area.

Analyses of water samples from 88 wells and 3 springs in the Edwards aquifer show that the water in the freshwater zone is of a significantly better quality than the level established for public water systems. However, trace concentrations of organic compounds were detected in many of the analyses. Analyses of water samples collected from two wells in Bexar County and eight wells in Uvalde County showed concentrations of tetrachloroethylene in excess of 5 micrograms per liter. In 1986, samples were collected from wells along the “bad-water” line to detect changes in water quality as the potentiometric head in the Edwards aquifer changed.

Note: Large-format versions of the plates for this report are available at: https://www.edwardsaquifer.org/wp-content/uploads/2019/05/1988_Ozuna-etal_1986HydrologicData.pdf