Technical Reports Document Library

This report presents results of the Edwards Aquifer Authority’s (EAA’s) Edwards Aquifer Data Collection Program for calendar year 2012. During 2012, the EAA collected a wide variety of Edwards Aquifer data, including
• Groundwater level data;
• Precipitation measurement data;
• Groundwater recharge data;
• Groundwater discharge and usage data;
• Water quality data from groundwater,
surface water, and springs; and
• Significant events affecting the
Edwards Aquifer.

Water levels at the Bexar County (J-17) index wellwere below the historical mean for the entire year. The maximum level of 666.8 feet above msl at J-17 occurred during March, and the low of 637.6 feet above msl occurred in August.

Other wells in the region exhibited similar behavior with regard to lower than normal water levels. The Comal County observation well had an annual high water level slightly above the historical mean high. However, for most of the year, this well also exhibited lower than normal water levels.

In 2012, rainfall amounts were above the mean in Bexar, Comal, and Hays counties and below the mean in Medina and Uvalde counties. In general, the region received between 60 and 129 percent of normal precipitation during the year, with the west receiving the lower rainfall totals and the east receiving the higher rainfall totals.

Total estimated recharge to the Edwards Aquifer was below normal in 2012. Recharge for the year was estimated at 313,500 acre-feet, compared with the period-of-record (1934–2012) median annual recharge value of 556,900 acre-feet. Recharge in 2012 was below the period-of-record median value for all basins, except for the Blanco River Basin, which was above the median.

In calendar year 2012, total groundwater discharge from the Edwards Aquifer through wells and springs was estimated at 687,033 acre-feet. This amount is below the median total discharge of 692,900 acre-feet for the period of record (1934–2012).

Discharge from wells in 2012 was estimated to be 384,685 acre-feet, approximately 56,885 acre-feet above the 327,800 acre-foot period of record (1934–2012) median. The lowest annual estimated discharge from wells for the period of record was 101,900 acre-feet in 1934, and the highest was 542,400 acre-feet in 1989.

Discharge from springs in 2012 was estimated at 302,348 acre-feet, somewhat below the period of record median of 379,900 acre-feet. The lowest annual discharge from springs for the period of record (1934–2012) was 69,800 acre-feet in 1956, and the highest was 802,800 acre-feet in 1992. Spring discharge in 2012 was the fifteenth lowest discharge on record.

In 2012, the EAA collected water quality samples from 95 wells (some wells sampled multiple times), 12 streams (some sampled in more than one location), and five spring groups. Samples collected for the year are summarized below by sample type and location.

Sample-Collection Summary, Calendar Year 2012

Bacteria Samples
• 313 samples collected at 77 wells
• 79 samples collected at four spring groups
• 20 samples collected at 11 stream sites

Metals Samples
• 110 samples collected at 64 wells
• 82 samples collected at five spring groups
• 17 samples collected at ten stream sites

Nitrate-Nitrite as Nitrogen
• 351 samples collected at 91 wells
• 81 samples collected at five spring groups
• 20 samples collected at 11 stream sites

Volatile Organic Compounds
• 102 samples collected at 61 wells
• 82 samples collected at five spring groups
• one sample collected at one stream site

Semivolatile Organic Compounds
• 29 samples collected at nine wells
• 80 samples collected at four spring groups
• Three samples collected at three stream sites

Pesticide and/or Herbicide Compounds
• 43 samples collected at 37 wells
• 82 samples collected at five spring groups
• 17 samples collected at ten stream sites

Polychlorinated Bi-Phenyls
• 39 samples collected at 36 wells
• 82 samples collected at five spring groups
• 17 samples collected at ten stream sites

Pharmaceuticals and Personal Care Products
• Seven samples collected at seven wells
• Three samples collected at three spring groups
• Two samples collected at two stream sites

In calendar year 2012, seven sanitary sewer system overflows occurred in Bexar County, the volume of one of which was considered significant, one moderate, three minor, and two negligible. The significant overflow occurred in October, the moderate in March, and the remaining five in April, May, September, and December (two). The largest overflow, approximately 111,350 gallons, occurred between October 14 and 15 east of Bulverde Road near the Santa Lucia and Montebello Road intersection in northern Bexar County. The moderate overflow, approximately 84,500 gallons, occurred on or about March 7 near Cloud Top Road, west of Blanco Road in northern Bexar County. The remaining overflows, which ranged between approximately 1,500 and 17,500 gallons per event, occurred between IH-10 to the west, and U.S. 281 to the east, both north and south of Loop 1604. The EAA responded to each event, taking a series of samples for the major and moderate events to determine whether a bacterial plume could be detected in the Edwards Aquifer.