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The average estimated annual ground-water recharge to the Edwards aquifer in the San Antonio area, Texas, from 1934 through 1988 was 635,500 acre-feet. Recharge in 1988 was 355,500 acre-feet, which is the fifteenth smallest estimated annual recharge since 1934. The maximum annual recharge of 2,003,600 acre-feet occurred in 1987, and a minimum annual recharge of 43,700 acre-feet occurred in 1956.

The calculated annual discharge from the Edwards aquifer by wells and springs in 1988 was 926,400 acre-feet, which is the third largest calculated annual discharge since 1934. 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.

Water levels in many of the wells during 1988 fluctuated above to near the mid-point between record high and low levels, reflecting an above to near average volume of ground water in storage in the aquifer during most of the year. In 1987, substantial increases occurred during the late spring and early summer, after which water levels remained above average in most of the area. Water levels then remained above to near average throughout 1988. Analyses of water samples from 56 wells and 3 springs in the Edwards aquifer show that the water quality in the freshwater zone is significantly better than the level established for public water systems. However, trace concentrations of organic compounds were detected in many of the analyses. In 1988. samples were collected and analyzed from wells transecting the “badwater” line and no significant changes in water quality were detected 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/2019/05/1989_Nalley_1988HydrologicData.pdf