USGS - science for a changing world

Water-Chemistry Monitoring

Historical water-chemistry data will be used in conjunction with data collected as part of this study. Water chemistry samples will be collected from monitoring wells installed as part of this study, including two multiple-well monitoring sites (monitoring different depths in the aquifer) and eight shallow monitoring wells. Samples will also be collected from about 15 existing wells (locations to be determined). These samples will be analyzed for chemical and isotopic constituents to help evaluate the regional source(s), flowpath(s), and age(s) of water from wells. This information will be used to help characterize the groundwater-flow system and document differences in water chemistry, both areally and vertically within the basin.

Go to the Interactive Map

map of sites in the San Antonio Creek Valley where groundwater quality samples have been and/or are being taken by the USGS

Well sites in the San Antonio Creek Valley where groundwater chemistry samples have been and/or are being taken by the USGS. Map image is the intellectual property of Esri and is used herein under license.

Proposed Water-Chemistry Sampling


collecting groundwater sample in glass bottle that will be tested for quality

Water chemistry samples will be collected, transmitted, analyzed, and archived in accordance with procedures outlined in the USGS National Field Manual for the Collection of Water-Quality Data.

Water-chemistry data will be collected from newly installed monitoring wells, including the two multiple-well monitoring sites and eight shallow monitoring wells installed in 2015 and 2016. Samples will also be collected from about 15 existing production wells (locations to be determined). Because surface-water infiltration is a major source of groundwater recharge, surface-water samples will be collected from streamflow-gaging stations and analyzed for similar constituents as the groundwater samples. Newly collected data will be augmented with historical water chemistry data available throughout the study area.

Detailed Listing of Chemical Analyses

  • Dissolved oxygen
  • Specific conductance
  • pH
  • Water temperature
  • Alkalinity
  • Deuterium (Hydrogen-2), also called heavy hydrogen
  • Oxygen-18
  • Strontium isotopes
  • Tritium (Hydrogen-3), radioactive isotope: half-life of 12.32 years
  • Carbon-13, stable isotope
  • Carbon-14, radioactive isotope: half-life of 5,730 ± 40 years
  • Nitrogen
  • Argon
  • Methane
  • Aluminum
  • Antimony
  • Arsenic
  • Barium
  • Boron
  • Bromide
  • Cadmium
  • Calcuim
  • Chloride
  • Chromium (total)
  • Fluoride
  • Iodide
  • Iron
  • Lead
  • Lithium
  • Magnesium
  • Manganese
  • Molybdenum
  • Potassium
  • Silica
  • Sodium
  • Strontium
  • Sulfate
  • Total dissolved solids
  • Uranium
  • Vanadium
  • Ammonia
  • Nitrate
  • Nitrite
  • Orthophosphate
  • Phosphorous

Laboratories Performing Analyses: