Technical Reports Document Library

The average estimated annual groundwater recharge to the Edwards Aquifer in the San Antonio region from 1934 through 1998 was approximately 683,100 acre-feet. Recharge in 1998 was approximately 1,142,300 acre-feet, which was well above the regional average. The lowest annual recharge of 43,700 acre-feet occurred in 1956, and the highest annual recharge of 2,486,000 acre-feet occurred in 1992.

Estimated annual discharge from the Edwards Aquifer through wells and springs in 1998 was 917,600 acre-feet. The lowest annual discharge through wells and springs was 388,800 acre-feet, which occurred in 1955. Spring discharge from the Edwards Aquifer for 1998 was calculated at 464,100 acre-feet or 51 percent of the total discharge. Groundwater pumping accounted for 453,500 acre-feet of water discharged from the Edwards Aquifer in 1998. In general, water level data during 1998 reflected a slight increase in water recharging the aquifer, as well as an increase in pumping relative to 1997.

Results of the Authority’s 1998 water quality monitoring program illustrate the continued excellent quality of water in the Edwards Aquifer. In 1998, the Authority collected water quality samples from wells, springs and stream basins, which were analyzed for major ions, nutrients, minor element metals, pesticides, herbicides, and VOC’s. Laboratory analyses of samples from several wells contained minor element metal concentrations slightly above the MDL. No
compounds were detected in 1998 above MCL concentrations. Laboratory analyses of the surface water samples collected in 1998 indicated no detectable concentrations of pesticides, herbicides, or VOC’s. Overall, results of the 1998 water quality sampling and analysis program illustrate the continued excellent quality of water in the Edwards Aquifer.