Groundwater is an important resource and needs to be protected from contamination. Using age dating, we can determine how connected groundwater is with the surface of the earth and because of this, just how vulnerable it may be to contamination.

We will show examples of the Alameda Creek watershed (Livermore Valley) and how surface water infiltrates the ground to become groundwater. We can study the formation and movement of groundwater using age dating. The radioactive decay of tritium (3H, half-life = 12.4 yr.) to stable helium-3 (3He) can be used to accurately tell how long the water has been underground. By measuring groundwater ages, we can see where and how fast the groundwater is moving. Areas of young groundwater (less than a few years old) locate zones that need the greatest protection from surface contamination.

Careers in water resources include many disciplines. A mixture of geology, chemistry, biology, physics and engineering forms the backbone of the field. Delivering water to people is also a business. Projects need plans and budgets, information has to be communicated, and many people have to be brought together in decision making. Sample collection and monitoring of the environment is a large effort. Construction and maintenance of increasingly complex equipment requires people with broad technical training. Careers in water resources can be rewarding, fun and extremely important to society. Everybody likes clean water!

Speaker Bios

Dr. Bryant Hudson

G. Bryant Hudson is a physicist in the Chemistry and Materials Science Directorate at LLNL. He completed a Ph.D. in physics at Washington University in St. Louis, Missouri working on early solar system chronologies. In 1981 he joined LLNL as a postdoctoral fellow studying isotopic tracers of environmental processes and continued on as a full time LLNL scientist developing noble isotope tracer techniques for diagnostic measurements of nuclear explosions. With the end of nuclear testing, he extended these noble gas tracer techniques to tracking the movement of groundwater. His research interests are in isotope geochemistry, rare isotopes in the environment including helium and tritium, and noble gas mass spectrometry. His main hobbies are ceramics, photography and gardening.

Dr. Sarah Palmer

Sarah Palmer is teacher Environmental Science and Technology for the Tri-Valley ROP (Regional Occupational Programs) at Foothill and Livermore High Schools. Dr. Sarah Palmer is currently teaching Environmental Science and Technology for the Tri-Valley ROP (Regional Occupational Programs) at Foothill and Livermore High Schools.

She holds a B.A. degree in Biology and Political Science from New York University and a Ph.D. in cell physiology and biochemistry from University of Toronto. In her career she has worked as a data technician at Goddard Space Flight Center, NASA and completed a post-doctoral research appointment at the Cancer Research Laboratory at UC Berkeley. Dr. Palmer worked as a Research and Development/Sales and Marketing liaison for a medical diagnostics firm, and taught biology, developmental biology, botany, zoology, ecology, immunology, physiology, and evolution at: UC Berkeley, CSU Hayward, Mills College, Holy Names College, and Las Positas College. She has also been a coordinator for the American Chemical Society's U. S. National Chemistry Olympiad for the past 5 years and help coordinate the Environmental Pathway for Foothill High School. Her hobbies are scuba diving and bicycling and her favorite job is being a mom.


  • General Water Terms
  • Aquifer: a water saturated zone of sand gravel or rock
  • Aquitard: an impermeable or confining layer of clay or rock
  • Artesian well: a well drilled down into a deep aquifer that is under pressure, bringing the level of the well water higher than the surrounding water table, perhaps even causing it to "pump" itself
  • Confined aquifer: an aquifer sandwiched between aquitards
  • Leaching: downward transport through the ground of dissolved or suspended minerals, fertilizers and other substances by water
  • Overdraft: removing water from an aquifer faster than it can be recharged
  • Porosity: water holding capacity in the spaces in a substance or substrate (such as sand, gravel, or clay)
  • Permeability: the ease of water movement through a substrate (this depends on the pore sizes and shapres of openings)
  • Recharge: the natural or human induced percolation of water into an aquifer for replenishment
  • Unconfined aquifer: an aquifer that has no upper confining layer
  • Water table: the upper surface of the zone of saturation in the ground
  • Watershed: region where water that runs off ridges, mountains, or highlands flows to a common outlet or drainage
  • Zone of saturation: area where all available spaces within rocks and the soil are filled with water
  • Hydrological (Water) Cycle Terms
  • Evaporation- water changing from liquid to vapor and going up into the atmosphere
  • Transpiration- water evaporating from plants
  • Condensation- water vapor molecules coming together to form a liquid
  • Precipitation- rain, snow, etc.
  • Runoff- water flowing down a hill, mountain, or field into a lake, stream, or other body of water
  • Infiltration- the absorption of water into the ground
  • Percolation- water working its way deeper into the ground to an aquifer
  • Age-Dating Terms
  • Isotopes: Two or more atoms having the same number of protons (the same element), but having different numbers of neutrons and hence a different mass. Naturally occurring chemical elements are usually mixtures of isotopes.
  • Radioactive isotopes: Atoms that disintegrate by the emission of particles or electromagnetic radiation (photons). In the process, the nucleus of the atom is transformed with a change in the number of neutrons and protons.
  • Beta decay: A specific type of radioactive decay where and electron is ejected and a neutron is transformed into a proton.
  • Tritium: An isotope of hydrogen with one proton and two neutrons. Tritium is radioactive with a half-life of 12.4 years. Tritium decays by beta decay and becomes a stable atom of helium, specifically, 3He that has 2 protons and one neutron. Most helium in nature is 4He (2 protons and two neutrons).
  • Half-life: The time it takes for one half of the atoms present in a sample to decay to something else. After one half-life, one half of the atoms of the original type are left.
  • Mass spectrometer: This is an instrument that can separate and measure individual isotopes. The mass spectrometer discussed in this talk consists of an ion source, a magnet and an ion detector. The ions are formed and accelerated in the ion source. The magnet bends the path of the ion beam depending on the mass of the ion. The detector measures when ions of a particular mass arrive.
  • Examples of Common Infectious Agents Found in Water
  • (Just when you thought it was safe to go back in the water!)
  • Protozoa
  • Giardia
  • Cryptosporidium
  • Helminths
  • Ascaris (roundworm)
  • Trichuris (whipworm)
  • Taenia (tapeworm)
  • Bacteria
  • Shigella
  • Salmonella
  • Cholera
  • E. coli
  • Legionella
  • Campylobacter
  • Viruses
  • Enteroviruses
  • Polioviruses
  • Coxsackie
  • Norwalk
  • Hepatitis A
  • Rotaviruses