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The average estimated annual ground-water recharge to the Edwards aquifer in the San Antonio area, Texas, from 1934 through 1989 was 628,000 acre-feet. Recharge in 1989 was 214,400 acre-feet, which is the tenth 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 1989 was 766,500 acre-feet, which is the fifteenth 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 1989 fluctuated near the midpoint between record high and low levels, reflecting a near average volume of ground water in storage in the aquifer during most of the year. In 1989, substantial increases occurred during the late winter and early spring, after which water levels remained near average in most of the area.

Water samples from 71 wells and 3 springs in the Edwards aquifer were analyzed for more than 50 properties or constituents, most of which affect the suitability of the water for domestic use. Concentrations of constituents in water from the freshwater zone did not exceed the maximum contaminant levels established for public water systems. However, trace concentrations of organic compounds were detected at five wells. In 1989, samples were collected and analyzed from wells transecting the freshwater/saline-water interface.