Technical Reports Document Library

The average estimated annual groundwater recharge to the Edwards Aquifer in the San Antonio area from 1934 through 1997 was 676,000 acre-feet. Recharge in 1997 was 1,135.000 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.

The estimated annual discharge from the Edwards Aquifer through wells (excluding irrigation discharge for Bexar, Medina, and Uvalde counties) and springs in 1997 was 684,700 acre-feet. The lowest annual discharge through wells and springs was 388,800 acre-feet, which occurred in 1955. Water-level data during 1997 reflected a general increase in water recharging the aquifer and a decrease in pumping during the year.

Results of the Authority’s 1997 water-quality monitoring program illustrate the continued excellent quality of water in the Edwards Aquifer. In 1997, the Authority collected water-quality samples from wells, springs and stream basins, which were analyzed for major ions, minor elements, pesticides, herbicides, volatile organics/aromatics, and nutrients. Laboratory analyses of well samples indicated no detectable levels of any volatile organic compounds. Laboratory analyses of samples from several wells contained minor element concentrations slightly above the minimum analytical detection limit for these constituents, but these values are extremely low in magnitude. Laboratory analyses of the surface-water samples collected in 1997 indicated no evidence of detectable concentrations of pesticides, VOCs or other constituents or parameters in excess of typical standards.