Instrumenting the Vadose Zone - the Gee Legacy.

A soil physicist’s interest in the Vadose zone focuses mainly on the transport of mass and energy in that zone.  Heat, water and solutes move downward and upward, and we would like to know how much moves and how fast they move.  The instruments used to measure the fluxes and driving forces for flow are critical for obtaining a correct picture of these important processes.   Glendon Gee made major contributions to the science of measuring these fluxes and forces.  This started with his PhD work using neutron attenuation to measure linked transport of heat and water in soil, and later included novel ways of measuring water potentials of desert soils, low cost weighing lysimeters, and finally simple and inexpensive passive capillary lysimeters.  This presentation will mention Glendon’s early work on linked transport and neutron attenuation, but will then focus on water potential measurement in dry soils and water flux measurement in dry environments.  Lysimeter theory will be discussed, and the current state of the work Glendon started in these areas will be assessed.