Data

Information about existing drinking water standards and health advisories for the compounds analyzed here can be found at this link.

PESTICIDES

Pesticides are used on a variety of landscapes from residential lawns to ranchland to golf courses. Most pesticides applied to these landscapes are water soluble and can infiltrate into the subsurface via fractures and sinkholes. These pesticides then travel through the aquifer and discharge at the springs. Details on pesticide analyses for this project can be found here.

For more information on pesticides, below are some useful links:

• http://pmep.cce.cornell.edu/profiles/extoxnet/index.html
• http://www.pesticideinfo.org/Search_Chemicals.jsp
• http://pmep.cce.cornell.edu/index.html
• http://ca.water.usgs.gov/pnsp/

VOLATILE ORGANIC COMPOUNDS

Volatile organic compounds (VOCs) include constituents of gasoline such as toluene, benzene, and methyl tert-butyl ether. Other VOCs include chloroform, a byproduct from the addition of chlorine to water, and tetrachloroethene, a metal degreaser and dry cleaning solvent. Chloroform and tetrachloroethene have been detected in multiple samples at low levels in Barton Springs in 2003. A list of volatile organic compounds analyzed can be found here.

For more information on volatile organic compounds see:

• http://sd.water.usgs.gov/nawqa/vocns/

NUTRIENTS

Although nutrients occur naturally in the environment, there are numerous anthropogenic sources as well. These sources include fertilizer, animal manure, and wastewater. Excess nutrients in streams and lakes can cause eutrophication (excessive growth of algae), resulting in the reduction of dissolved oxygen in water. A list of nutrients analyzed can be found here.

PHARMACEUTICALS

Pharmaceuticals are considered an emerging contaminant because of the recent recognition of their introduction into the environment by humans. A list of pharmaceuticals analyzed can be found here.

MAJOR IONS

The concentration of major ions in the springs can be a useful tool for understanding aquifer processes and the flow path the water takes from the contributing creeks through the aquifer and out the springs. For example, the concentration of magnesium in the water relative to the amount of calcium in the water can provide information about the time the water had spent in contact with the limestone aquifer before discharging at the springs. A list of major ions analyzed can be found here.

TRACE METALS

Ground water often contains trace concentrations of metals, which naturally leach from rocks and soils. There are numerous anthropogenic sources of metals, however, which can enrich ground-water concentrations above naturally-occurring levels. In the urban environment, these sources might include roadway, parking lot, and roof runoff, landfills leachate, waste water, and fertilizers.

CONDUCTIVITY

Conductivity is a measure of water's capacity to carry an electrical current, which is a direct reflection of the concentration of dissolved solids in the water. The conductivity of rain water is low compared to that of ground water, and therefore the dilution of aquifer water by infiltrated surface water can be detected through the measurement of spring water conductivity. After a storm event, a pulse of rainwater moving through the aquifer can be detected at the springs through a sudden drop in conductivity. A subsequent increase in conductivity indicates that the rainwater component of the spring water is diminishing. The conductivity of Main Barton Spring within the past 7 days can be found here.

DISCHARGE, TEMPERATURE, AND TURBIDITY

These are physical parameters of the springs that are measured every fifteen minutes at Main Barton Spring and are broadcast over the web every one to four hours. This data for the past 31 days can be found here.