Water-quality observations of the San Antonio segment of the Edwards aquifer, Texas, with an emphasis on processes influencing nutrient and pesticide geochemistry and factors affecting aquifer vulnerability, 2010–16

Abstract

Graphs showing relation between strontium-87/strontium-86 isotopic ratio and magnesium to calcium molar ratio and time series of strontium-87/strontium-86 isotopic ratio measured in groundwater samples collected from the San Antonio segment of the Edwards aquifer, south-central Texas, 2013-16..

Fecal pollution source characterization in the surface waters of recharge and contributing zones of a karst aquifer using general and host-associated fecal genetic markers

“…36 Helotes Creek is a relatively small stream that flows on the west side of Bexar County with a stream length of 24 km approximately. 37 Studies focusing on the water quality of San Geronimo and Helotes Creeks are limited 31 and, to our knowledge, field studies to evaluate the fecal contamination of waters in these two Creeks were not carried out previously.…”

“…3 The Edwards aquifer region can rapidly get recharged with surface waters and storm runoffs due to the presence of large voids and sinkholes in the recharge zone, signifying its vulnerability to contamination. 31 Several studies conducted on Edwards aquifer water quality have documented the nutrient contamination of water sources from anthropogenic agents. 31,32 However, studies focusing on microbial water quality in the Edwards aquifer region are limited.…”

“…31 Several studies conducted on Edwards aquifer water quality have documented the nutrient contamination of water sources from anthropogenic agents. 31,32 However, studies focusing on microbial water quality in the Edwards aquifer region are limited. 26 Furthermore, limited studies were conducted so far on understanding the relationship between nutrients and fecal markers in different environmental processes and land management practices of Edwards aquifer.…”

Barton Springs segment of the Edwards (Balcones Fault Zone) Aquifer, central Texas

“…Water quality of the Edwards Aquifer, and in the Barton Springs segment of the Edwards Aquifer, is very good, with few samples approaching the U.S. Environmental Protection Agency's (EPA) maximum concentration levels (MCLs) for drinking water Smith et al, 2001;Anaya et al, 2016;Opsahl et al, 2018). The Barton Springs segment of the Edwards Aquifer groundwater generally has low TDS (<500 mg/L) calcium-bicarbonate (Ca-HCO3) facies with trends toward high TDS (>1000 mg/L) and sodium-chloride (Na-Cl) in the saline part of the Edwards Aquifer (Fig.…”

“…However, Upper Barton Spring is affected by anthropogenic contaminants (nutrients and pesticides) likely related to its highly urbanized watershed area. Similarly, in the San Antonio segment, wells completed in the unconfined urban areas had elevated nitrate and pesticide concentrations (Opsahl et al, 2018). Isotopes of strontium ( 87 Sr/ 86 Sr) can be used to identify anthropogenic sources of recharge for the Barton Springs segment of the Edwards Aquifer watersheds (Christian et al, 2011).…”