Isotope studies can be useful in hydrology in answering the following questions:

1. What is the source of the water?
2. What is the age of the water?
3. What is the source of solutes (including contaminants) in water?

1. What is the source of the water? (back to top)

• What is the moisture source of precipitation?
       see text at Oxygen/Hydrogen

• What is the recharge source of groundwater?
       see text at Oxygen/Hydrogen and at Noble Gases

• Has the water experienced evaporation?
       see text at Oxygen/Hydrogen

2. What is the age of the water? (back to top)

• How do you select the proper isotopic system for dating groundwater?
       see “Dating Groundwater with Isotopes,” by Brenda Ekwurzel

• How can I date recent groundwaters (<100 years)?
       see text on Tritium (3H) under Hydrogen , Helium-3 and Lead.

• How can I date old groundwater (100 to 1000 years old)?
       see text on Carbon-14 and “Locating Recharge Zones with Isotopes,” by Christopher Eastoe

• How can I date very old groundwater (>10,000 years)? (36Cl) (I129)
       see text on Helium-4 , Chlorine-36 and Iodine-129

3. What is the source of solutes (including contaminants) in water? (back to top)

• What type of rocks or sediments has a water interacted with? (Sr, S, Pb)
       see Strontium , Sulfur and Lead

• What is the flowpath of a water? (Sr, S, Tucson basin study article)
       see Strontium , Sulfur and “Locating Recharge Zones with Isotopes,” by Christopher Eastoe

• What is the source of organic contamination in groundwater?
       see text under Carbon

• What is the source of lead contamination?
       see Lead

• What is the source of nitrate in groundwater? (N isotopes)
       see text under Nitrogen

• What is the source of salinity in water?
       see Strontium , Chlorine and SAHRA work on the Solute Balance of the Rio Grande